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  • Calcium  (98)
  • Springer  (98)
  • 1980-1984  (98)
  • 1950-1954
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  • 1
    Electronic Resource
    Electronic Resource
    Effects of vitamin D and parathyroid hormone on cyclic AMP production by bone cells isolated from rat calvariae (1984)
    Springer
    Calcified tissue international 36 (1984), S. 320-326 
    Details
    ISSN: 1432-0827
    Keywords: Calcium ; Vitamin D deficiency ; 1,25(OH)2D3 ; Parathyroidectomy ; Parathyroid hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Studies presented here were designed to investigate further the basis for an impaired cAMP response to parathyroid hormone (PTH) in osteoblastlike calvarial bone cells isolated from vitamin D-deficient rat pups. The goal was to perturb Ca, PTH, and vitamin Din vivo in order to see which factors might be responsible for the impairedin vitro bone cell cAMP response. Pups either were parathyroidectomized (PTX) 3–5 days, implanted with osmotic minipumps delivering high doses of PTH, given repeated, high doses of 1,25(OH)2D3, or were D-deficient (-D, i.e., born and suckled by D-deficient mothers). Osteoblastlike bone cells, isolated by sequential enzyme digestion and centrifugation, were exposed to PTH for 5 min in the presence of a phosphodiesterase inhibitor. In bone cells isolated from -D rat pups, both basal and PTH-induced cAMP accumulation were significantly lower than in +D bone cells. Earlier, we had shown that two daily injections of -D pups with 50 ng 1,25(OH)2D3 restores this reduced bone cAMP response of -D pups toward normal. In the present study, neither basal nor PTH-induced bone cell cAMP accumulation was affected by subjecting D-replete pups to PTX, PTH infusion, or repeated high doses of 1,25(OH)2D3 despite the fact that each treatment markedly changed serum Ca or serum immunoreactive PTH. The results indicate that the impaired bone cell cAMP response seen in -D pups is not a direct result of chronic hypocalcemia and that the “heterologous desensitization” seenin vitro with added 1,25(OH)2D3 could not be duplicated byin vivo treatment of +D pups with supraphysiologic doses of 1,25(OH)2D3. Finally the lack of alteration in the bone cell cAMP response to PTHin vitro after chronic PTH infusionin vivo fails to support the notion that the impaired response in -D bone cells can be explained entirely by “homologous desensitization” induced by high circulating levels of PTH in the hypocalcemic, -D rat pup.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405337
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  • 2
    Electronic Resource
    Electronic Resource
    Assessment of anin vivo diffusion chamber method as a quantitative assay for osteogenesis (1984)
    Springer
    Calcified tissue international 36 (1984), S. 77-82 
    Details
    ISSN: 1432-0827
    Keywords: Osteogenesis ; Diffusion chambers ; Alkaline phosphatase ; Calcium ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The alkaline phosphatase activity and the calcium and phosphorus content of osteogenic tissue formedin vivo following the implantation of diffusion chambers loaded with rabbit bone marrow cells is reported. (In this study the term osteogenic includes osteoblastic and chondroblastic.) Chambers examined 14–70 days after implantation revealed progressive accumulation of mineral. Alkaline phosphatase activity increased until day 30 and declined thereafter. The osteogenic potential of the marrow cells decreased with increasing weight (age) of the cell donor rabbit when measured either as the percentage of chambers containing osteogenic tissue or as the amount of calcium, phosphorus, or alkaline phosphatase activity within the chambers. The results confirm that measurements of these parameters in tissue formed by cells incubated in diffusion chambersin vivo may be used as a method for assay of osteogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405297
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  • 3
    Electronic Resource
    Electronic Resource
    Blood/bone disequilibrium: IV. Reciprocal effects of calcium and phosphate concentrations on ion fluxes (1980)
    Springer
    Calcified tissue international 32 (1980), S. 229-236 
    Details
    ISSN: 1432-0827
    Keywords: Bone ; Ion influxes ; Calcium ; Phosphate ; Exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Quantitative measurements were made of the ion fluxes of calcium and phosphate into and from calvaria (mouse or rat) when clamped in specially designed micro-Ussing chambers. The effects of varying concentrations of calcium were examined on the influx and efflux of calcium and of its counterion, phosphate. A comparable series of experiments was performed with varying phosphate concentrations. Both ions, as their concentrations increased, depressed their own influx, increased their own efflux, and significantly increased the equilibrium concentration, E/K, supported by the calvaria. Similarly, both ions, as their concentrations increased, affected the influx or efflux of their counterion only slightly but did depress the counterion's equilibrium level, E/K, significantly. In spite of these changes it was shown that calvaria effectively buffered the medium at physiological concentrations of calcium and phosphate. The buffering capacity, however, was small, and the balance, E/K, was modified by small uptake or loss of either ion. The small size of the interacting mineral pool was confirmed by direct measurement of the rapidly exchanging fractions of both calcium or phosphate. They were only ∼1% of the total ions present. The significance of these findings is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408546
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  • 4
    Electronic Resource
    Electronic Resource
    Calcitonin and parathyroid hormone in newborn infants with fracture of the clavicle (1984)
    Springer
    Calcified tissue international 36 (1984), S. 357-360 
    Details
    ISSN: 1432-0827
    Keywords: Calcitonin ; Parathyroid hormone ; Calcium ; Newborn ; Fracture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Determinations of serum calcium (Ca), phosphorus (P), calcitonin (CT), and parathyroid hormone (PTH) were carried out in 36 full-term newborn infants with fracture of the clavicle (CF) and in 46 normal neonates (N). At the 6th hour of life the CF neonates demonstrated lower serum Ca and higher serum CT in comparison with normal infants. In the hours following, no significant differences between the two groups for the Ca levels were found, whereas serum CT remained significantly higher in the CF newborns at the 24th, 48th, and 72nd hour of life. Significant differences between normal and CF infants in the PTH serum levels were detected only at the 48th hour, when PTH was lower in the CF newborns. The results of this investigation indicate that the fracture of the clavicle is a significant and peculiar factor in stimulating CT secretion. Serum Ca level appeared to be controlled by CT rather than auto-regulating the secretion of the hormone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405346
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  • 5
    Electronic Resource
    Electronic Resource
    Mineral loss in cortical and trabecular bone during high-dose prednisone treatment (1984)
    Springer
    Calcified tissue international 36 (1984), S. 269-273 
    Details
    ISSN: 1432-0827
    Keywords: Bone loss (osteopenia) ; Calcium ; Corticosteroids (glucocorticosteroids) ; Fluoride ; Vitamin D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary To evaluate the effect of prednisone and triple treatment (sodium fluoride, calcium, and vitamin D) on trabecular and cortical bone serial bone mineral content (BMC) measurements were made at a metaphyseal (BMCD) and diaphyseal (BMCP) site on the forearm on 31 consecutive and previously bone-healthy patients scheduled for at least 24 weeks high-dose prednisone treatment. The patients were randomized into two further treatment groups: group I (n=16) received prednisone plus triple treatment and group II (n=15) received only prednisone. The two groups were similar with regard to age, sex, prednisone dose, and initial BMC. During 24 weeks treatment, BMCD (partially representing trabecular bone) and BMCP (mainly representing cortical bone) fell significantly and similarly, demonstrating that there is no preventive effect on bone mineral loss on the triple regimen. The BMC fall after 12 weeks was significantly more pronounced for metaphyseal (partially trabecular) than for diaphyseal (cortical) bone, whereas the values did not differ significantly after 24 weeks; this indicates a greater sensitivity to the hormone treatment of trabecular bone. In the entire group, the fall in BMC correlated positively with individual prednisone dose, significant at the diaphyseal site (r=0.39,P〈0.05), but not at the metaphyseal site (r=0.31, P=0.08). It is concluded that corticosteroid-induced osteopenia is a diffuse bone disease which affects trabecular as well as cortical bone, suggesting that BMC measured on the forearm reflects changes in bone mineral at other locations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405329
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  • 6
    Electronic Resource
    Electronic Resource
    Changes in plasma bone GLA protein during treatment of bone disease (1982)
    Springer
    Calcified tissue international 34 (1982), S. 121-124 
    Details
    ISSN: 1432-0827
    Keywords: Bone ; Calcium ; Metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Bone Gla protein (BGP) was measured in the plasma by radioimmunoassay (RIA) during treatment of 59 patients with bone diseases including Paget's disease (N=9), primary hyperparathyroidism (N=25), chronic renal failure (N=20), and cancer involving bone (N=5). Plasma BGP was increased above normal in all patients. BGP decreased in the patients with Paget's disease following the acute and chronic administration of salmon calcitonin. Plasma BGP was higher in women then in men with primary hyperparathyroidism. Following parathyroidectomy, BGP decreased in both sexes but the decrease was significant in women only. Plasma BGP was increased in patients with renal osteodystrophy and did not change after hemodialysis. In the patients with bone cancer, plasma BGP decreased during treatment of the attendant hypercalcemia with salmon calcitonin. Although plasma BGP and serum alkaline phosphatase (AP) levels were generally correlated in these studies, there were examples of dissociation between the two. The measurement of plasma BGP appears to provide a specific index of bone metabolism that may in some circumstances be more sensitive than serum alkaline phosphatase measurement. However, further studies are necessary to establish the clinical value of plasma BGP measurement by RIA in the management of patients with bone diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411221
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  • 7
    Electronic Resource
    Electronic Resource
    A fully automated and computerized system for simultaneous measurements of motility and phototaxis in Chlamydomonas (1983)
    Springer
    Archives of microbiology 135 (1983), S. 259-264 
    Details
    ISSN: 1432-072X
    Keywords: Phototaxis ; Motility ; Flagellate ; Chlamydomonas ; Sodium azide ; Calcium ; A 23 187
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A fully automated and computerized method for simultaneous measurements of motility and phototaxis of unicellular flagellates is described. Both systems are directly coupled with a homocontinuous culture. The motility measuring apparatus is equipped with a video camera and recorder for simultaneous single cell behaviour studies. First results of studies on the effects of the phototaxis inhibitor sodium azide and the Ca2+ conducting ionophore A23 187 on motility and phototaxis of Chlamydomonas are reported and correlated with video observations. These results demonstrate that the described systems give informations of whether phototaxis or motility or both are inhibited by chemicals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00413478
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  • 8
    Electronic Resource
    Electronic Resource
    The role of calcium in stalk development and in phosphate acquisition in Caulobacter crescentus (1984)
    Springer
    Archives of microbiology 138 (1984), S. 140-152 
    Details
    ISSN: 1432-072X
    Keywords: Caulobacter ; Prostheca development ; Stalk function ; Calcium ; Phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Calcium was found to stimulate stalk development in Caulobacter crescentus and to relieve the inhibition of development long known to be caused by phosphate. This suggested that phosphate inhibition could be attributed to its interaction with Ca2+, thereby depriving the cells of a factor that promoted development. Calcium was also found to promote phosphate acquisition by the cells, observed as acceleration of growth at extremes of phosphate concentration, as promotion of carbon-source utilization rather than storage, and as support for phosphate-dependent resistance to arsenate inhibition of growth. Cytological studies of dividing cells revealed that stalked siblings had greater access to exogenous phosphate for use in growth or for storage as polyphosphate, and that access of non-stalked sibling to phosphate was dependent on the length of the stalk of the dividing cell. It was concluded that the physiologic role of the stalk is enhancement of phosphate acquisition. The stimulatory role of calcium in this process was attributed to its support of stalk development and to its stabilization of internal membrane/cell envelope association within the cell-stalk juncture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00413014
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  • 9
    Electronic Resource
    Electronic Resource
    Elemental analysis of particles in fungal zoospores (1984)
    Springer
    Archives of microbiology 139 (1984), S. 102-104 
    Details
    ISSN: 1432-072X
    Keywords: Fungus ; Zoospore ; Blastocladiella ; Allomyces ; Gamma ; Particle ; Phosphate ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The elemental composition of gamma particles in zoospores ofAllomyces macrogynus andBlastocladiella emersonii was determined by use of energy dispersive X-ray analysis of glutaraldehyde fixed, thin section zoospores. Isolated preparations of gamma particles were also examined. Gamma particles contained no detectable elements. Similar sized, globular, electron dense cytoplasmic inclusions contained phosphorus and calcium. We suggest that previous studies assigning calcium and phosphorus to gamma particles may have been based on confusion of these two types of cytoplasmic inclusions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692722
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  • 10
    Electronic Resource
    Electronic Resource
    Rhythmic dentinogenesis in the rabbit incisor: Allometric aspects (1980)
    Springer
    Calcified tissue international 32 (1980), S. 45-53 
    Details
    ISSN: 1432-0827
    Keywords: Dentin ; Periodicity ; Allometry ; Calcium ; Sulfur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary We have described differences in the aspects of biological rhythms for calcium and sulfur deposition on the labial and lingual sides of the growing rabbit incisor, where growth occurs along a spiral axis. The calcium oscillations appear to be smoother on the labial side than on the lingual side. The lingual side is characterized by high-frequency rhythms with high amplitudes which possess the greatest percent of the power (Fourier analysis). These observations also reflect a difference in behavior of the mean Ca concentration across the labial and lingual sides. Sulfur rhythms on the labial side have higher amplitudes than those on the lingual side, but systematic differences in distribution of power between high and low frequencies is not as pronounced as in the case of Ca. The differences in Ca rhythms reflect differences in the growth rates of incisors on either side of the spiral axis. The labial side grows slightly faster than the lingual side, and its odontoblasts secrete Ca along the spiral axis and toward the pulp cavity at the same time. Thus the resultant direction of growth is more nearly opposite the extension of the occlusal end on the labial side, and Ca is consequently deposited over a wider area relative to that on the lingual surfaces. On the lingual side, Ca is deposited within a more limited area, and growth must therefore be continuous at high frequencies. The distribution of Ca on both sides of the tooth reflects these differences in growth rate and periodicity in two ways. First, given a unit area of tooth, the calcium concentration on the labial side is less than that of the lingual side. Second, whereas the calcium concentration on the labial side declines rapidly from the enamel-dentin junction to the pulp cavity, it is uniformly high across the lingual side because its growth is more continuous at high frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408520
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  • 11
    Electronic Resource
    Electronic Resource
    Effects of 1α-hydroxy vitamin D3 on the rachitic chick intestine: A comparison to the effects of 1,25-dihydroxyvitamin D3 (1980)
    Springer
    Calcified tissue international 32 (1980), S. 9-17 
    Details
    ISSN: 1432-0827
    Keywords: 1α-Hydroxy vitamin D3 ; 1,25-Dihydroxyvitamin D3 ; Calcium ; Transport ; Intestine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The timed sequence of events following the oral administration of 1α-hydroxy vitamin D3 (1αOHD3) to rachitic chicks was compared to that following a comparable dose of 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3). RNA polymerase activity was maximally increased 20% by 1αOHD3 within 1 to 2 h and returned to control values after 8 h. Alkaline phosphatase activity was stimulated by 4 h and was maximal (3- to 5-fold increase) at 24 h. Calcium binding protein (CaBP) was detected initially within epithelial cells at the proximal end of the villus (just above the crypt) 6 to 8 h after 1αOHD3 administration, in epithelial cells lining the proximal half of the villus by 24 h, and in epithelial cells along nearly the entire villus by 48 h. At no time did goblet cells contain CaBP. Serum calcium concentrations were significantly elevated in 2 h and maximal by 12 h (an increase of 3.6 mg/dl). Calcium accumulation by the intestinal mucosa in vitro was increased by 6 to 8 h and maximal (60% increase over controls) at 24 h. Phosphate accumulation by the intestinal mucosa in vitro was increased by 6 h and maximal (105% increase over controls) between 8 and 24 h. 1,25(OH)2D3 increased CaBP and calcium accumulation by 4 h, 2 h sooner than did 1αOHD3. 1,25(OH)2D3 decreased serum calcium levels and increased serum phosphate levels at 2 h unlike 1αOHD3. No difference in the effects of these compounds on alkaline phosphatase activity, RNA polymerase activity, and phosphate accumulation could be demonstrated. These results are consistent with the possibility that 1αOHD3 may not require conversion to 1,25(OH)2D3 for all of its biological effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408517
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  • 12
    Electronic Resource
    Electronic Resource
    In vitro perifusion for the study of parathyroid hormone secretion: Effects of extracellular calcium concentration and beta-adrenergic regulation on bovine parathyroid hormone secretion in vitro (1980)
    Springer
    Calcified tissue international 32 (1980), S. 19-27 
    Details
    ISSN: 1432-0827
    Keywords: Perifusion ; Parathyroid hormone ; In vitro ; Calcium ; Beta regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary An in vitro perifusion system was used to study parathyroid hormone (PTH) secretion in response to calcium (Ca) and beta-adrenergic agents. Perifused parathyroid tissue responded to changes in Ca within the physiologic range during experiments up to 5 h. There was rapid secretory stimulation after exposure to low Ca, with the maximum response being observed at 20 min. Normal bovine glands showed a Ca-independent nonsuppressible component of PTH release at concentrations of Ca above physiologic. 1-isoproterenol produced rapid stimulation of PTH release, the response being blocked by a beta antagonist. The maximum secretory response to either low Ca (0.5 mM) or 1-isoproterenol (10−5 M) was enhanced when the two stimuli were applied simultaneously. The response to isoproterenol was blocked by raising Ca to 2.5 mM. Although d,l-propranolol (10−4 M) caused mild suppression of PTH release at a Ca of 1.25 mM, it did not cause additional suppression at 2.5 mM Ca nor did it decrease the response to 0.5 mM Ca stimulation. The secretory response of the gland to low Ca was sustained at a level more than double the baseline rate. The response to isoproterenol was more transient, with a return to or toward baseline secretion within 60 min. These results suggest that beta agonists and low Ca have separate but related mechanisms for stimulating PTH release and may affect different pools of hormone. The perifusion system described is a relatively simple technique for assessing the kinetics and interactions of various stimulators of PTH secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408518
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  • 13
    Electronic Resource
    Electronic Resource
    Rhythmic dentinogenesis in the rabbit incisor: Circadian, ultradian, and infradian periods (1980)
    Springer
    Calcified tissue international 32 (1980), S. 29-44 
    Details
    ISSN: 1432-0827
    Keywords: Rabbit ; Dentin ; Calcium ; Sulfur ; Periodicity ; Circadian ; Ultradian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary We have identified a variety of biological rhythms involved in the apposition and mineralization of dentin in the rabbit incisor. Animals were injected during the day or night with lead acetate at 2-week intervals—to provide biological time markers in forming dentin—and transverse undecalcified sections of the lower incisors were prepared for electron microprobe analysis. The positions of the lead markers were identified, and the continuous distribution of calcium and sulfur was measured at 1 µm intervals between the markers. In thin sections stained with hematoxylin after decalcification, the widths of a series of structural increments (bands) were measured with an ocular micrometer. Fourier analysis of the data revealed spectra of structural and compositional rhythms with a range of periodicities which extended from a matter of hours [ultradian (〈24 h)] to days [infradian (〉24 h) and circadian (approximately 24 h)]. The structural and compositional rhythms appeared to be independent to the extent that they did not necessarily have the same periods, or amplitudes. Nor were there simple phase relationships between all of the rhythms. At some times, Ca and S fluctuations are inversely proportional (180° out of phase), but in other cases they are directly proportional or out of phase by varying degrees other than 180°. The analyses thus suggest that calcium and sulfur deposition (representing mineral and glycosaminoglycan deposition, respectively) are not simply inversely proportional, and that the hematoxylin-stained structural increments did not solely reflect differences in the distribution of the mineral components in dentin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408519
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  • 14
    Electronic Resource
    Electronic Resource
    Effects of magnesium ion on parathyroid hormone secretion in vitro (1980)
    Springer
    Calcified tissue international 32 (1980), S. 201-206 
    Details
    ISSN: 1432-0827
    Keywords: Magnesium ; Parathyroid hormone ; Secretion ; In vitro ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary In a well-defined in vitro perifusion system, the effects of extracellular magnesium concentration (Mg) on parathyroid hormone (PTH) secretion by bovine parathyroid tissue were examined. At Mg less than 0.8 mM, the ability of the glands to secrete hormone maximally in response to low calcium (Ca) stimulation was progressively impaired. Low Mg also impaired the ability of isoproterenol, dibutyryl cyclic AMP and theophylline to stimulate hormone release. The defect in hormone release at low Mg observed in vitro was analogous to the well-documented inhibition of secretion observed in vivo. Increases in Mg from 0 to 0.8 mM rapidly repaired the defect in hormone secretion. At Mg above 1.0 mM there was a Ca-like effect on hormone release, with a progressive decrease in secretion at increased Mg. Although its mechanism is not yet clear, the low Mg effect appears to impair principally the process of hormone release rather than its biosynthesis or storage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408542
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  • 15
    Electronic Resource
    Electronic Resource
    Effects of weight loss on serum 1,25-(OH)2-vitamin D concentrations in adults: A preliminary report (1984)
    Springer
    Calcified tissue international 36 (1984), S. 139-144 
    Details
    ISSN: 1432-0827
    Keywords: 1,25(OH)2-vitamin D ; Weight loss ; Phosphate ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary During a review of 42 metabolic studies in healthy women and men we observed that serum 1,25-(OH)2-D concentrations were directly correlated to the observed daily changes in body weight (r=0.68;P〈0.001) and to caloric intake/kg/day (r=0.39;P=0.01). These relationships could not be accounted for by related and physiologically expected changes in serum Ca or iPTH concentrations. However, serum 1,25-(OH)2-D concentrations were observed to be inversely correlated to serum PO4 levels (r=−0.44;P=0.004). In addition, serum PO4 levels were inversely correlated to the daily changes in body weight (r=−0.40;P=0.009). Since dietary sodium intake averaged 142 mmol/day, it is unlikely that the observed changes in weight were the result of changes in salt and water balance. Thus it seems reasonable to speculate that serum 1,25-(OH)2-D concentrations may vary directly with energy balance, as reflected by changes in body weight. This effect may be mediated by alterations in PO4 metabolism. The accurate assessment of serum 1,25-(OH)2-D levels thus appears to require several measurements over time periods during which body weight is stable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405309
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  • 16
    Electronic Resource
    Electronic Resource
    Hypervitaminosis D in the chick embryo: Comparative study on the activity of various vitamin D3 metabolites (1984)
    Springer
    Calcified tissue international 36 (1984), S. 392-400 
    Details
    ISSN: 1432-0827
    Keywords: Vitamin D ; Chick embryo ; Bone ; Calcium ; Phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Chick embryos were injected in the yolk sac at various ages with various doses of different vitamin D3 metabolites. Serum concentrations of total calcium and inorganic phosphate were determined 24 h after the injection and histological and electron microscopic studies of the tibiae were conducted 3–6 days after. Confirming previous results, the injection of 1,25(OH)2D3 was found to produce significant hypercalcemia and hypophosphatemia. The dose required to produce these effects decreased with age: 100 ng on the 9th day, 50 ng on the 11th, and 10 ng on the 15th. This finding is interpreted as resulting from the fact that the specialized cells in the chorionic epithelium which are considered to be involved in mineral resorption from the shell differentiate between the 11th and 13th days. Although no bone changes were observed in embryos injected before the 11th day, a rim of unmineralized trabeculae (osteoid) was observed at the periphery of the cortex of the tibial diaphysis in the embryos which had been injected after that age. Thus, in embryos injected on the 11th day with 100 ng 1,25(OH)2D3, the trabeculae formed between the 11th and 14th day remained unmineralized until the 15th or 16th day at which time they completed their mineralization. In the embryos injected on the 14th day, the alterations were more severe and could be produced with doses 10 times smaller than those required when the injections were made on the 11th day. At all ages, the doses that produced an osteoid rim also induced hypercalcemia and hypophosphatemia. The electron microscopical study of the osteoid trabeculae showed that osteoblasts and osteocytes had normal cytological characteristics and that the bone matrix did not present changes other than the reduction in mineral deposition. While the above findings do not exclude a direct action of 1,25(OH)2D3 on bone cells as the mechanism of osteoid formation, they do underline the importance of the humoral changes at least as partial determinants of this phenomenon. The activities of various vitamin D metabolites were compared using as parameter the threshold-dose required to produce a rim of unmineralized trabeculae in the tibia of 14–15 days embryos (T-D). The most active metabolite appeared to be 1,25(OH)2D3 (T-D: 10 ng); it was followed by 1,24,25(OH)3D3 (T-D: 100 ng) and 1,25,26(OH)3D3 (T-D: 100 ng). Vitamin D3 itself (T-D: 100 µg), 25(OH)D3 (T-D: 2.5µg) and 24,25(OH)2D3 (T-D: 5 µg) produced similar responses but only when administered in much larger doses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405351
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  • 17
    Electronic Resource
    Electronic Resource
    Effect of 1,25-dihydroxyvitamin D3 on osteopenia induced by prednisolone in adult rats (1982)
    Springer
    Calcified tissue international 34 (1982), S. 253-257 
    Details
    ISSN: 1432-0827
    Keywords: Prednisolone ; Calcium ; Bone ; Corticoid osteopenia ; Vitamin D metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Adult male rats were fed a diet containing 0.15% calcium, 0.3% phosphorus, and either 100, 50, or 20 mg of prednisolone per kg of diet. All these levels of prednisolone led to osteopenia, decreased intestinal absorption of calcium, slightly lower serum calcium and phosphorus, and a decreased level of serum 1,25-dihydroxyvitamin D3. Exogenous parenteral 1,25-dihydroxyvitamin D3 corrected steroid-induced changes in serum calcium and phosphorus, but could not completely correct the low intestinal calcium transport; nor did it prevent the development of osteopenia. The prednisolone-induced osteopenia seems at least in part to be caused by impaired intestinal calcium transport. The impaired calcium transport may be the result of low levels of 1,25-dihydroxyvitamin D3 and a direct effect of presnisolone on the intestine.
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    URL: http://dx.doi.org/10.1007/BF02411246
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    On the role of calcium in chemotaxis and oscillations of dictyostelium cells (1982)
    Springer
    European biophysics journal 9 (1982), S. 131-136 
    Details
    ISSN: 1432-1017
    Keywords: Chemotaxis ; Calcium ; Oscillation ; Dictyostelium ; Ionophore
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Migration of differentiated cells to a capillary containing cyclic AMP was enhanced in the presence of 1 mM CaCl2 and was virtually absent in the presence of 1 mM EGTA. Furthermore, the cells contracted and extended pseudopods to a capillary filled with the calcium ionophore A 23187. At short distances, migration to the tip of the capillary was observed. The ionophore also induced transient decreases of the optical density of suspended cells indicating changes of cell shape. These findings support the hypothesis that cyclic AMP-binding to cell surface receptors causes a local influx of calcium ions. These in turn lead to an increase of the cytosolic calcium concentration and subsequently to an activation of cell migration. Perturbing pulses of the ionophore induced permanent phase shifts of free-running light scattering oscillations. This result indicates that cytosolic calcium is an intrinsic component of the oscillatory system.
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    URL: http://dx.doi.org/10.1007/BF00539112
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  • 19
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    Calcium-mediated enhancement of the cyclic AMP response in cultured bone cells (1981)
    Springer
    Calcified tissue international 33 (1981), S. 409-416 
    Details
    ISSN: 1432-0827
    Keywords: Bone Cells ; Cyclic AMP ; Calcium ; Parathyroid hormone ; Prostaglandin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary We have examined the influence of extracellular Ca2+ on cyclic AMP metabolism in an osteoblast-enriched population of bone cells isolated from the calvaria of rat fetuses. The cyclic AMP1 response to stimulators of cyclic AMP formation (PTH and PGE2), but not basal cyclic AMP levels, increased progressively as the extracellular Ca2+ concentration was raised from 0.2 to 4.0 mM. The response to changes in extracellular Ca2+ were rapid (within 3.5 min), and the level of responsivity that characterized each Ca2+ concentration persisted for at least 6 h when the Ca2+ concentration was kept constant. The effect of Ca2+ spanned the entire time course of PTH action, was not accompanied by altered excretion of cyclic AMP from the cells, and was evident at low as well as at high hormone concentrations. Ca2+ augmented the action of PTH in the presence as well as in the absence of cyclic AMP phosphodiesterase inhibitors, and failed to decrease cyclic AMP phosphodiesterase activity in the short term. Mn2+ and, to a smaller degree, Ba2+ substituted for Ca2+ in promoting the cyclic AMP response to PTH. Verapamil, an inhibitor of Ca2+ penetration, blunted the Ca2+-mediated increments in the cyclic AMP response, and the divalent cation ionophore A23187 enhanced these increments. These results indicate that Ca2+ and other cations are positive effectors of the stimulated cyclic AMP response in isolated bone cells. Accumulation into an as yet unknown cellular compartment may be required for the cation effect. The data are most consistent with enhancement of adenylate cyclase reactivity as the mode of cation action.
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    URL: http://dx.doi.org/10.1007/BF02409464
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  • 20
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    Effects of a bone resorptive factor from human cancer ascites fluid on rat bone cell calcium and cyclic AMP (1980)
    Springer
    Calcified tissue international 30 (1980), S. 191-197 
    Details
    ISSN: 1432-0827
    Keywords: Bone cells ; Cyclic AMP ; Calcium ; Ascites fluid resorptive protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The effects of a bone resorptive protein isolated from human cancer ascites fluid on bone cell calcium and cyclic AMP were studied with fetal rat cells. The osteoclast-activating factor increased bone cell calcium uptake at 37°C and 4°C with no direct effects on calcium efflux. Concentrations of the resorptive factor that increased in vitro bone resorption and cell calcium uptake had no effect on cyclic AMP. The effects of the protein on calcium uptake were not specific for bone cells, and large increases were also observed in isolated fetal rat skin cells. These studies suggest that increases in the permeability of the cell membrane to calcium are involved in the mechanism of action of the ascites fluid resorptive protein.
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    URL: http://dx.doi.org/10.1007/BF02408627
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  • 21
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    In vitro effects of vitamin D3 metabolites on rat calvaria cAMP content (1980)
    Springer
    Calcified tissue international 30 (1980), S. 209-216 
    Details
    ISSN: 1432-0827
    Keywords: Calvarium ; cAMP ; Vitamin D3 metabolites ; Calcium ; Parathyroid hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Results from in vitro works suggest that 1,25- and 24,25-dihydroxyvitamin D3 (1,25-(OH)2D3 and 24,25-(OH)2D3) act on bone via different mechanisms. The present investigation was performed to study the effect of these two metabolites and of their precursor 25-hyxdroxyvitamin D3 (25-(OH)D3) on bone cAMP content in vitro. Rats' paired half calvaria were incubated under sterile conditions with one vitamin D3 derivative (10−13 to 10−9 M) or with ethanol (0.005 ml for 15 min to 24 h in 1 ml medium containing 0, 0.2, 1, 2, or 3 mM calcium. In some experiments: (a) cycloheximide (10−5M) was added simultaneously with the vitamin D3 metabolites; (b) 1–84 bPTH (5 × 10−8 M) was added for 5 or 15 min at the end of the 24 h incubation. Calvaria were immersed in 1 ml TCA 5% 4°C and homogenized. The cAMP was extracted with diethylether and measured by a competitive protein binding assay. Results bring further evidence for a particular effect of low doses of 24,25-(OH)2D3 (10−9 to 10−12M) and of 25-(OH)D3 (10−9 to 10−11M) on bone, different from that of 1,25-(OH)2D3: cAMP content was higher in 24,25-(OH)2D3- or 25-(OH)D3-treated and lower in 1,25-(OH)2D3-treated calvaria than in ethanol-treated ones with 1 mM calcium. The 1,25-(OH)2D3 effect persisted in calcium-free medium whereas 25-(OH)D3 and 24,25-(OH)2D3 effects could not be observed with 0 mM nor with 3 mM calcium. The required duration of the preincubation (over 1 h) as well as the inhibitory action of cycloheximide may suggest an involvement of protein synthesis in the vitamin D3 metabolites effects. Neither 1,25-(OH)2D3 nor 24,25-(OH)2D3 affected the PTH-induced increase in bone cAMP content.
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    URL: http://dx.doi.org/10.1007/BF02408630
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  • 22
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    Oral 1,25(OH)2D3: An effective prophylactic treatment for glucocorticoid osteopenia in rats (1983)
    Springer
    Calcified tissue international 35 (1983), S. 107-110 
    Details
    ISSN: 1432-0827
    Keywords: Calcium ; Glucocorticoid ; Vitamin D ; Osteoporosis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Eighty-eight adult male Sprague-Dawley rats were given a diet with either (a) 0.5% Ca and 0.6% P or (b) 0.01% Ca and 0.6% P. Osteopenia was created by adding prednisolone to the diet. The prophylactic effect of oral 1,25(OH)2D3 on the osteopenia was studied. It was found that prednisolone osteopenia in the rat was associated with defective Ca absorption. By giving an oral dose of 1,25(OH)2D3, it was possible to maintain normal Ca absorption during prednisolone treatment and to prevent the bone loss. No significant hypercalcemia or any kidney calcifications were seen. These results are in contrast to earlier findings, in which subcutaneous administration of 1,25(OH)2D3 failed to prevent prednisolone osteopenia because of its tendency to increase bone resorption.
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    URL: http://dx.doi.org/10.1007/BF02405014
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  • 23
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    31P nuclear magnetic resonance spectroscopic evidence for ternary complex formation of fetal dentin phosphoprotein with calcium and inorganic orthophosphate ions (1983)
    Springer
    Calcified tissue international 35 (1983), S. 815-818 
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    ISSN: 1432-0827
    Keywords: 31P NMR spectroscopy ; Phosphoprotein ; Dentin ; Calcium ; Inorganic orthophosphate ; Bovine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The single phosphoprotein of fetal calf dentin, having a molecular weight of approximately 94,000 and a phosphorus content of 8% (w/w), was examined by31P NMR spectroscopy. The single resonance at 3.7 ppm at pH 10 and its chemical shift during acid titration established the phosphomonoester nature of the organic phosphorus moiety. During titration of the phosphoprotein with CaCl2 in the presence of inorganic orthophosphate ions, line broadening for the orthophosphate resonance was both phosphoprotein- and calcium-dependent, indicating ternary complex formation. The data indicate that the phosphoprotein of fetal calf dentin binds both calcium and inorganic orthophosphate ions and therefore has the requisite physical chemical properties necessary for it to facilitate the heterogeneous nucleation of a Ca-PO4 solid phase from solution during tissue mineralization.
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    URL: http://dx.doi.org/10.1007/BF02405129
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    Electromagnetic modulation of biological processes: Influence of culture media and significance of methodology in the Ca-uptake by embryonal chick tibiain vitro (1984)
    Springer
    Calcified tissue international 36 (1984), S. 167-174 
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    ISSN: 1432-0827
    Keywords: Electromagnetic field ; Bicarbonate ; Phosphate ; Calcium ; Fluoride ; Osteogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The present studies are aimed at establishing molecular correlations in the interaction of very low frequency electromagnetic fields with biological systems. Ca-uptake by chick embryo tibia rudiment in short-term culture was a useful model. Tibiae of 8- to 10-day-old chick embryos were incubated 60 min in simplified culture media in the presence of45Ca at 37.5±0.5°C either inside or outside pulsating electromagnetic fields. Radioactivity count in the medium was the most accurate method for determining Ca-uptake by the rudiment. The effect of the fields on the Ca-uptake depended markedly on the chemical composition of the culture medium: bicarbonate was indispensable; glucose or sucrose was important; phosphate was potentiating; ethanol, Mg2+, and NaF were stimulating. The field had no effect in (a) blank medium without tibia, (b) tibiae that had been altered by fixation with aqueous glutaraldehyde, (c) nonliving artificial systems endowed with great or small ion sorption capacity. The unique bicarbonate effect with living systems and the passive behavior of nonliving ion sorbing systems prompt the suggestion that the electromagnetic field probably couples with specific processes, such as a bicarbonate-dependent Ca2+ ATPase and the active ion transport, at the cell membrane level. The molecular mechanisms remain to be established.
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    URL: http://dx.doi.org/10.1007/BF02405313
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    Calcium distribution in freeze-dried enamel organ tissue during normal and altered enamel mineralization (1984)
    Springer
    Calcified tissue international 36 (1984), S. 596-603 
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    ISSN: 1432-0827
    Keywords: Calcium ; Ameloblasts ; X-ray microanalysis ; Transport ; Frozen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Energy dispersive X-ray microanalysis was applied to freeze-dried blocks of enamel organ tissue to determine levels of calcium in various celular regions. The tissue blocks were dissected free from adjacent forming enamel following injection of cobalt or fluoride ions, both of which temporarily inhibit enamel mineralization. In all control and experimental specimens there was an increasing gradient of calcium from the stratum intermedium cells to the distal ends of the ameloblasts. Calcium levels were significantly reduced near the distal ends of the ameloblasts following cobalt or fluoride injection as compared with controls. It is suggested that evidence of an intercellular buildup of calcium near the distal ends of the ameloblast supports a controlling function of these cells. The changes in calcium levels are correlated with alterations in mineralization known to occur in the adjacent enamel of the model systems employed.
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    URL: http://dx.doi.org/10.1007/BF02405373
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    Ultrastructure, function and composition of smooth muscle (1983)
    Springer
    Annals of biomedical engineering 11 (1983), S. 579-588 
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    ISSN: 1573-9686
    Keywords: Smooth muscle ; Electron probe analysis ; Calcium ; Myosin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Filamentous myosin is present in both relaxed (myosin light chains unphosphorylated) and contracted (light chains phosphorylated) vascular smooth muscle. The organization of myosin and actin filaments and the insertion of the latter on cytoplasmic and plasma membrane bound dense bodies is consistent with a mini sarcomere-like organization and a sliding filament mechanism of contraction in smooth muscle. Mitochondria are high capacity, low affinity Ca stores in smooth muscle. They do not play a role in the regulation of cytoplasmic Ca2+ at physiological levels. The localization and Ca content of the junctional sarcoplasmatic reticulum (SR) is consistent with this organelle being the major intracellular source of activator Ca released by excitatory transmitters. Repeated contractions in the absence of extracellular Ca2+ (thought to represent recycling of intracellular activator Ca2+) can be demonstrated if the excitatory agent is not allowed to remain in contact with the smooth muscle throughout relaxation; the demonstration of “recycling” is facilitated if the efflux of cellular Ca2+ is blocked. The rise in total cytoplasmic calcium measured with electron probe analysis during a maintained (30 min) contracture in rabbit portal-anterior mesenteric vein smooth muscle (∼0.9 mmol/kg dry cytoplasm) is greater than the amount of Ca that could be bound to calmodulin.
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    URL: http://dx.doi.org/10.1007/BF02364087
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    Total body bone mineral and lean body mass by dual-photon absorptiometry (1981)
    Springer
    Calcified tissue international 33 (1981), S. 365-368 
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    ISSN: 1432-0827
    Keywords: Absorptiometry ; Osteoporosis ; Spinal bone ; Bone mineral content ; Neutron activation ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Dual-photon absorptiometry using153Gd (44 and 100 keV) was used to measure the bone mineral content (BMC) of the trunk and of the total body (TBBM) in 7 volunteers with no overt bone disease. These values were compared to those obtained with partial-body neutron activation of calcium (trunk Ca). The trunk Ca seemed to represent best a 60 × 30 cm area; the correlation coefficient with the corresponding BMC in that area was 0.97 (SEE ⋍ 7%). Trunk Ca was also highly correlated with TBBM (r=0.96; SEE=8%) and with radius BMC (r=0.92; SEE=11%), but the correlations with the BMC of smaller subareas of the trunk were lower (r⋍0.9; SEE ∼ 12%). The BMC of the lumbar spine was only moderately correlated with trunk Ca, radius BMC and TBBM (r ∼ 0.82; SEE ∼ 18%), and only slightly more associated with trunk BMC (r ∼ 0.88; SEE ∼ 14%). The BMC of the combined lumbar-thoracic spine showed higher correlations with trunk Ca, radius BMC and TBBM (r ∼ 0.87; SEE ∼ 13%), and trunk BMC (r=0.93; SEE ∼ 10%). An accurate and sensitive measure of spinal status requires a direct measurement of that area.
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    URL: http://dx.doi.org/10.1007/BF02409457
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    Effects of age and sex on the regulation of plasma 1,25-(OH)2-D by phosphorus in the rat (1981)
    Springer
    Calcified tissue international 33 (1981), S. 477-484 
    Details
    ISSN: 1432-0827
    Keywords: 1,25-(OH)2-D ; Calcium ; Phosphorus ; Sex ; Age
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Dietary phosphate deprivation in women, but not men, is accompanied by a fall in plasma PO4 and a rise in plasma 1,25-(OH)2-vitamin D concentrations. In contrast, young male rats exhibit a fall in plasma PO4 and a rise in plasma 1,25-(OH)2-D concentrations in response to PO4 deprivation. To evaluate whether age and sex influence basal plasma 1,25-(OH)2-D levels and their regulation by PO4 deprivation, plasma 1,25-(OH)2-D, PO4, and Ca levels were measured in male and female rats ranging in age from 6 weeks to 6 months while they were eating normal or low PO4 diets for 1 to 16 days. Similar observations were also made in 6-week-old castrated male and female rats, males replaced with testosterone, and females replaced with estradiol. Basal plasma 1,25-(OH)2-D levels were higher in 6-week-old males (228±76 pmol/l) than in 6-week-old females (148±62 pmol/l;P〈0.01) and declined by age 11 weeks to stable levels averaging about 100 pmol/l without sex difference. Dietary PO4 deprivation resulted in a three-to fourfold increase in plasma 1,25-(OH)2-D concentrations regardless of age and sex, accompanied by a correlated rise in serum Ca concentrations. Castration of 6-week-old males and females eliminated the sex difference in basal plasma 1,25-(OH)2-D levels and appeared to enhance the elevation of plasma 1,25-(OH)2-D concentrations in response to PO4 deprivation in females. Although gonadal hormones may modify basal plasma 1,25-(OH)2-D levels, they are not required for the augmentation of plasma 1,25-(OH)2-D levels in response to PO4 deprivation.
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    URL: http://dx.doi.org/10.1007/BF02409477
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    Factors in response to treatment of early postmenopausal bone loss (1981)
    Springer
    Calcified tissue international 33 (1981), S. 575-581 
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    ISSN: 1432-0827
    Keywords: Osteoporosis ; Vitamin D ; Bone mineral ; Estrogen ; Aging ; Thiazide ; Fluoride ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Bone mineral content (BMC) was measured by125I photon absorptiometry every 3 months in 264 normal females (45–54 years) over a 2-year period together with serum samples for calcium, phosphate, magnesium, creatinine, alkaline phosphatases, potassium, and protein. A 48-h urinary calcium and creatinine measurement was obtained. The subjects were divided into 7 treatment groups and 3 placebo groups. Five of the treatments (thiazide, vitamin D3, fluoride + vitamin D3, fluoride, and 1αD3) were ineffective at the doses used; the annual loss of compact bone was 1.5–2.2% (-X=1.8%), similar to the loss seen with placebos. Estrogen and estrogen + thiazide, in contrast, produced a 1.34% annual increase of BMC. The subjects were divided into groups with low, medium, and high initial BMC. Also, individual regressions for bone change were calculated and the subjects were divided into groups of responders, maintainers, and losers (annual change of 〉0%, 0 to −1%, and 〉−1%, respectively). The initial BMC status did not consistently affect bone or biochemical responses to the therapeutic agents. Estrogen was effective even in subjects with high BMC, whereas the other agents did not inhibit bone loss even in subjects with low initial BMC. Virtually all subjects responded to estrogen positively; in contrast we could not identify a subset of “responders” with any of the other treatments. Time since menopause appeared to influence the bone changes, although it was not a significant effect given the sample size. Bone loss in groups not treated with estrogens was 2%/year at 20 months after menopause with a decline to 1.3%/year at 45 months post-menopause. There was no apparent decline in the bone response to estrogen during the first 4 years after menopause, and in fact bone response tended to increase with time.
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    URL: http://dx.doi.org/10.1007/BF02409494
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    Ultrastructural localization of calcium in the mandibular condylar growth cartilage of the rat (1980)
    Springer
    Calcified tissue international 30 (1980), S. 27-34 
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    ISSN: 1432-0827
    Keywords: Ultrastructure ; Calcium ; Cartilage ; Vesicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The potassium pyroantimonate technique was utilized for the selective subcellular localization of calcium in the mandibular condylar cartilage of 1-day-old rats. Electron dense calcium pyroantimonate precipitates were localized principally in mitochondria and at the cell membrane of the chondrocytes. In addition, small intracellular vesicles 0.1–0.2µm in diameter were observed in proximity to the cell membrane of chondrocytes of the mid-hypertrophic zone. The results suggest that these vesicles were being extruded from the cell into the extracellular matrix. Energy-dispersive analysis by X-rays confirmed that calcium is the principal cation of the electron-dense precipitates.
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    URL: http://dx.doi.org/10.1007/BF02408603
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    Effects of pyrophosphate and diphosphonates on the dissolution of hydroxyapatites using a flow system (1980)
    Springer
    Calcified tissue international 31 (1980), S. 153-159 
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    ISSN: 1432-0827
    Keywords: Hydroxyapatite ; Dissolution ; Pyrophosphate, Diphosphonates ; Calcium ; Phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Pyrophosphate and diphosphonate ions have been said to diminish the dissolution of hydroxyapatite crystals, because they lower the equilibrium concentrations of calcium and phosphate ions in the bulk solution around hydroxyapatite crystals in a closed system. However, in a closed system these effects are not necessarily due to an effect on dissolution alone. In this paper we have used a continuous flow system to study the effects of pyrophosphate and two diphosphonates, ethane-1-hydroxy-1,1-diphosphonate and dichloromethane diphosphonate, on the dissolution of hydroxyapatite. All three compounds decreased markedly the rate of dissolution of hydroxyapatite as well as the exchangeable pools of calcium and phosphate ions around the cystals.
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    URL: http://dx.doi.org/10.1007/BF02407176
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    Characterisation of the Egeria densa Planch. leaf symplast (1983)
    Springer
    Planta 158 (1983), S. 320-328 
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    ISSN: 1432-2048
    Keywords: Calcium ; Egeria ; Fluorescent probe ; Ions, group II ; Symplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The hydrophyllic dyes fluorescein glutamic acid, fluorescein glutamylglutamic acid (F(Glu)2), fluorescein hexaglycine, fluorescein leucyldiglutamyl-leucine and 6-carboxyfluorescein are unable to pass the plasmalemma in leaves of E. densa. However, when injected into single cells the dye conjugates of molecular weight 665 dalton or less move freely from cell-to-cell. This intercellular movement presumably occurs via the plant symplast. Movement of F(Glu)2 from the injected cell occurs with greatly reduced frequency when Ca2+, Mg2+ or Sr2+ are injected into the cell immediately prior to the dye. The fraction of dye injections leading to movement declines with increasing group II ion concentration in the electrode tip, up to 10 mM. Sodium and K ions do not affect dye movement. When dye injection is delayed 30 min after Ca2+ injection, dye movement is no longer inhibited. Thus the cells recover from the Ca2+ injection, indicating that the ion does not cause major cell damage. Recovery from Mg2+ injection is not complete within 60 min. Treatment of leaves with chemicals expected to raise the concentration of free intracellular group II ions, notably the mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxyphenyl hydrazone, the inhibitor of mitochondrial Ca2+ uptake trifluralin, or the ionophore A23187 also inhibits dye movement, while the calmodulin inhibitor trifluoperazine does not. Cytoplasmic streaming is inhibited by Ca2+ or Mg2+ injection and by the metabolic inhibitors. However when streaming is stopped by cytochalasin B, dye movement is not inhibited. Hence steaming is not necessary for dye movement. Thus the cytoplasmic concentration of free group II ions may directly regulate the permeability of the plant symplast.
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    URL: http://dx.doi.org/10.1007/BF00397334
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    Control of plasma 1,25-(OH)2-vitamin D concentrations by calcium and phosphorus in the rat: Effects of hypophysectomy (1981)
    Springer
    Calcified tissue international 33 (1981), S. 485-488 
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    ISSN: 1432-0827
    Keywords: 1,25-(OH)2-D ; Hypophysectomy ; Calcium ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The mechanism by which dietary phosphate deprivation elevates plasma 1,25-(OH)2-D levels is not known. To evaluate the role of the pituitary in regulating plasma 1,25-(OH)2-D concentrations, the responses of plasma 1,25-(OH)2-D to dietary phosphate deprivation and, separately, to dietary calcium deprivation were evaluated in intact and hypophysectomized male rats. Among intact and hypophysectomized rats eating normal diets, plasma 1,25-(OH)2-D levels averaged 228±76 and 148±62 pmol/1, respectively (P〈0.01). During dietary phosphate deprivation, plasma 1,25-(OH)2-D levels rose to 1160±260 in intact rats and fell to 90±26 pmol/l in hypophysectomized rats (P〈0.001). By contrast, during dietary calcium deprivation, plasma 1,25-(OH)2-D levels rose in both intact and hypophysectomized animals to 856±107 and 742±279 pmol/l, respectively (NS). In response to dietary phosphate deprivation, serum calcium concentrations rose as 1,25-(OH)2-D concentrations rose in intact rats but remained at control levels in hypophysectomized rats. These results support the hypothesis that a pituitary hormone acting either directly or indirectly on the kidney mediates the increase in plasma 1,25-(OH)2-D during dietary phosphate deprivation. The hypercalcemia that occurs in rats during dietary phosphate deprivation appears to depend on the elevation of plasma 1,25-(OH)2-D.
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    URL: http://dx.doi.org/10.1007/BF02409478
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    Calcium homeostasis and bone pathology in magnesium deficient rats (1980)
    Springer
    Calcified tissue international 31 (1980), S. 231-238 
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    ISSN: 1432-0827
    Keywords: Magnesium ; Bone ; Calcium ; Parathyroid gland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Calcium homeostasis and bone pathology were studied in weanling rats fed a low (70 ppm) magnesium diet for 2–21 days. The rats developed significant, progressive hypercalcemia after 6 days on the diet. The increase in blood calcium was accompanied by progressive hypoactivity of the parathyroid gland (PTG), as determined by histologic and morphometric analyses. Thus hyperactivity of the PTG could not have been responsible for the hypercalcemia observed. Histologic examination of femora and humeri from magnesium-deficient rats showed progressive subperiosteal hyperplasia, consisting of undifferentiated osteoprogenitor cells and fibrous tissue, after 7 days of deficiency. The presence of unmineralized osteoid tissue in the metaphyses indicated that mineralization was not proceeding normally. The alterations in differentiation of osteoprogenitor cells, together with the failure of mineralization, resulted in significantly lower rates of bone formation (as measured by fluorochrome labeling) in the magnesium-deficient rats. Basophilic cementing lines and inactive osteocytes in the cortices of bones from magnesium-deficient rats indicated that bone resorption was also severely reduced in magnesium deficiency. We postulate that bone magnesium depletion (66% by day 21) has a direct negative effect on osteoblastic and osteocytic activity, and may explain, in part, the decreased responsiveness of bone to parathyroid hormone (PTH) that has been observed in magnesium-deficient animals.
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    URL: http://dx.doi.org/10.1007/BF02407186
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    Equilibrium dialysis and ultrafiltration studies of calcium and phosphate binding by human salivary proteins. Implications for salivary supersaturation with respect to calcium phosphate salts (1982)
    Springer
    Calcified tissue international 34 (1982), S. 531-538 
    Details
    ISSN: 1432-0827
    Keywords: Saliva ; Calcium ; Phosphate ; Ion-binding ; Supersaturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Previous ultrafiltration studies indicated that up to one-half of the calcium and two-thirds of the phosphate in human salivary secretions may be bound by salivary proteins. Since this binding is an important variable in determining the extent of salivary supersaturation with respect to calcium phosphate salts, and since the amount of binding reported is surprisingly large, calcium and phosphate ion-binding by salivary macromolecules has been reexamined. From experiments using equilibrium dialysis, it was found that (1) the fraction of salivary calcium involved in macromolecular complexes ranges from a few percent for unstimulated secretions, to no more than about 10% for stimulated glandular salivas, and (2) salivary proteins do not bind phosphate ions to any significant extent. These findings, and experiments using an improved ultrafiltration membrane, indicate that the earlier results were artifacts of the ultrafiltration technique. Fractionation of salivary proteins, followed by equilibrium dialysis measurements, showed that the anionic proline-rich proteins and a basic proline-rich glycoprotein are responsible for most of the calcium binding now observed. The finding that macromolecular complexes of salivary calcium and phosphate have been overestimated in the past, leads to the conclusion that salivary calcium and phosphate ion activities in stimulated salivary secretions may be up to 50 to 100% higher than previously thought. Revised values were therefore used to recalculate the degree of salivary supersaturation with respect to calcium phosphate salts. The results indicate that stimulated salivary secretions are supersaturated with respect to dicalcium phosphate dihydrate; this is a substantially greater degree of supersaturation than previously reported.
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    URL: http://dx.doi.org/10.1007/BF02411299
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    Benzo(B)Thiophene-2-Carboxylic acid: Calcium uptake and cyclic AMP production in isolated bone cells (1984)
    Springer
    Calcified tissue international 36 (1984), S. 194-199 
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    ISSN: 1432-0827
    Keywords: Benzo(B)Thiophene-2-Carboxylic Acid ; Bone cells ; Calcium ; Cyclic AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The purpose of the present study was to investigate the mechanism of action on bone of Benzo(B)Thiophene-2-Carboxylic Acid (BL-5583). BL-5583, at a dose range of 0.01–100 µg/ml, inhibited spontaneous as well as A23187 and PTH-induced bone resorption in tissue culture. This compound also decreased calcium uptake in both osteoclastic and osteoblastic enriched bone cell populations obtained by sequential collagenase digestion of 1–2 day newborn rat calvariae. The decrease occurred after a 5 min. incubation with45Ca and BL-5583. The effective dose range was 0.01–100 µg/ml. No effect on leucine incorporation or lactic acid production by bone cells was observed. BL-5583 also induced a transient decrease in calcium uptake in skin cells isolated from fetal rats by collagenase digestion, suggesting a lack of tissue specificity for this compound. No effect on cyclic AMP in isolated bone cells was observed with the same dose range that produced a calcium effect.
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    URL: http://dx.doi.org/10.1007/BF02405317
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    In vitro precocious accumulation of calcium and matrix vesicles formation in young cartilage cells: Specific effects of corticosteroids (1984)
    Springer
    Calcified tissue international 36 (1984), S. 702-710 
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    ISSN: 1432-0827
    Keywords: Corticosteroids ; Cartilage ; Organ culture ; Calcium ; Matrix vesicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The present study examined the effects of various corticosteroid and noncorticosteroid hormones upon the ultrastructure of chondroprogenitor cells and chondroblasts in an organ-culture system of late fetal condylar cartilage. Corticosteroids, (triamcinolone acetonide, dexamethasone, corticosterone) at concentrations of 10−6–10−8M stimulated markedly a precocious formation of matrix vesicles by chondroblasts. This stimulation was accompanied by a significant accretion of calcium complexes intra- and extracellularly in both the chondroprogenitor cell population and chondroblastsin vitro, as well as in the newly induced matrix vesicles. Nonglucocorticoid steroids (progesterone, estradiol, testosterone, cortexolone) did not evoke similar effects. Progesterone and testosterone, however, seemed to adversely affect the ultrastructure of the cartilage cells, whereas estradiol appeared to have a favorable effect on the morphology of cultured condylar cartilage.
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    URL: http://dx.doi.org/10.1007/BF02405393
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    Effect of phosphate on phosphatidylserine-mediated calcium transport (1982)
    Springer
    Calcified tissue international 34 (1982), S. 43-48 
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    ISSN: 1432-0827
    Keywords: Calcium ; Phosphate ; Phosphatidylserine ; Transport ; Mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Experiments were performed to study the effect of inorganic phosphate (Pi) on phosphatidylserine-mediated Ca2+ transport utilizing two- and three-compartment lipid-aqueous phase model systems. When the three-compartment model was used, the rate of Ca2+ transport from an aqueous donor compartment to an aqueous receiver compartment, separated by a nonaqueous phospholipid phase, was determined. This experiment showed that the rate of Ca2+ transport was proportional to the phosphatidylserine concentration and the pH. Pi modulated the rate of Ca2+ transport; even when the Pi concentration of the donor aqueous phase was low, there was a marked enhancement of transport. To determine whether the Pi-mediated rise in the Ca2+ transport rate was due to an increase in the uptake of Ca2+ into the lipid phase, or to an increase in the ability of the lipid phase to release Ca2+, a two-compartment model was used. It was found that the ability of the phosphatidylserine phase to take up Ca2+ increased as the Pi concentration of the aqueous donor phase was raised. With the increase in Ca2+ uptake there was a concomitant elevation in the rate of Ca2+ transport into an aqueous receiver phase. However, Pi did not stimulate Ca2+ release from the phosphatide. Thus it was concluded that Pi enhanced the interaction between Ca2+ and phosphatidylserine, possibly by forming a Ca-phospholipid-Pi complex. Once this interaction had taken place, Ca2+ release into the aqueous receiver compartment was independent of the Pi concentration.
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    Calcium and gibberellin-induced elongation of lettuce hypocotyl sections (1981)
    Springer
    Planta 152 (1981), S. 450-456 
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    ISSN: 1432-2048
    Keywords: Calcium ; Cell elongation ; Gibberellin ; Lactuca ; pH and growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between calcium ions and gibberellic acid (GA3)-induced growth in the excised hypocotyl of lettuce (Lactuca sativa L.) was investigated. The short-term kinetics of growth responses were measured using a linear displacement transducer. Test solutions were added either as drops to the filter paper on which the hypocotyl stood (“non-flow-past”) or by switching solution flowing past the base of hypocotyl (“flow-past”), resulting in differences in growth behavior. Drops of CaCl2 added at a high concentration (10 mM) inhibited growth within a few minutes. This inhibition was reversed by ethylenediaminetetraacetic acid (EDTA). Drops of EDTA or ethyleneglycol-bis(2-aminoethylether)-tetraacetic acid caused a rapid increase in growth rate. Growth induced by EDTA was not further promoted by GA3. A continuous H2O flow resulted in growth rates comparable to those in response to GA3. Addition of CaCl2 to the flow-past medium inhibited growth and this inhibition was reversed by a decrease in CaCl2 concentration. The growth rate was found to be a function of CaCl2 concentration. When a constant CaCl2 concentration was maintained by the flow-past medium, a shift in pH from 5.5 to 4.25 had no obvious effect on hypocotyl elongation. Gibberellic acid was found to reverse the inhibitory effect of CaCl2, causing an increase in growth rate similar to that found previously when GA3 was added to hypocotyls grown in H2O under non-flow-past conditions. We propose that gibberellin controls extension growth in lettuce hypocotyl sections by regulating the uptake of Ca2+ by the hypocotyl cells.
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    The role of calcium ions in phytochrome-mediated germination of spores of Onoclea sensibilis L. (1984)
    Springer
    Planta 160 (1984), S. 12-20 
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    ISSN: 1432-2048
    Keywords: Calcium ; Calmodulin ; Germination (spore) ; Onoclea ; Phytochrome and Ca2+ ; Pteridophyta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytochrome is confirmed to be the photoreceptor pigment in the germination response of Onoclea sensibilis L. by demonstrating red-far-red (R-FR) photoreversibility. External Ca2+ is required for this response with a threshold at a submicromolar concentration. Ethylene glycol-bis(β-amino-ethyl ether)-N,N,N′,N′-tetraacetic acid, La3+ and Co2+ reversibly inhibit germination. Lanthanum only inhibits germination when applied before or during irradiation, indicating that the external Ca2+ requirement is transient, although in the absence of Ca2+ the R-stimulated system remains maximally poised to accept the ion for over 4 h after irradiation. The ability to respond to Ca2+ 4.1 h after R-irradiation is not reversed by FR-irradiation, indicating that Ca2+ transport has been uncoupled from phytochrome. Barium and Sr2+, but not Mg2+ can substitute for Ca2+. Artificially increasing the concentration of intracellular free Ca2+ with the ionophore A 23187 stimulates germination in the dark. The Ca2+-calmodulin antagonists, trifluoperizine and chlorpromazine, reversibly inhibit germination. Calcium is required in phytochrome-mediated fern spore germination; it may be acting as a second messenger.
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    Diurnal changes in the flux of calcium toward meristems and transpiring leaves in tomato and maize plants (1981)
    Springer
    Planta 151 (1981), S. 265-271 
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    ISSN: 1432-2048
    Keywords: Calcium ; Cation exchange ; Lycopersicon esculentum ; Rhythm ; diurnal Transport (calcium) ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tomato (Lycopersicon esculentum Mill. cv. Moneymaker) and maize (Zea mays L. cv. spec.) plants were supplied with 45Ca-labeled nutrient solutions for a period of 8 or 16 h in the dark, in the light, or in a light-dark régime. Plant parts were analyzed for 45Ca content. The partitioning of 45Ca between mature leaves and meristems was shown to be affected by the presence of light. The transport of 45Ca to meristems was higher in a dark period than in a comparable light period. Experiments with excised tomato shoots yielded similar distribution patterns of 45Ca over leaves and meristems, thus excluding root pressure as the main driving force for the enhanced import of 45Ca into the meristems in the dark. Results are discussed in terms of cation-exchange transport and competition between the various calcium sinks.
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    Localization of membrane-associated calcium following cytokinin treatment in Funaria using chlorotetracycline (1981)
    Springer
    Planta 152 (1981), S. 272-281 
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    ISSN: 1432-2048
    Keywords: Bryophyta ; Bud formation (moss) ; Calcium ; Chlorotetracycline ; Cytokinin ; Funaria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have investigated the changes in membrane-associated calcium that occur during cytokinin induced bud formation in Funaria hygrometrica Hedw. using the fluorescent Ca2+-chelate probe chlorotetracycline (CTC). In the target caulonema cells a localization of CTC fluorescent material becomes evident at the presumptive bud site 12 h after cytokinin treatment. By the time of the initial asymmetric division this region is four times as fluorescent as the entire caulonema cell. Bright CTC fluorescence remains localized in the dividing cells of the bud. To relate the changes in CTC fluorescence to changes in Ca2+ as opposed to membrane-density changes we employed the general membrane marker N-phenyl-1-naphthylamine (NPN). NPN fluorescence increases only 1.5 times in the initial bud cell. We conclude that the relative amount of Ca2+ per quantity of membrane increases in this localized area and is maintained throughout bud formation. We suggest that these increases in membrane-associated Ca2+ indicate a localized rise in intracellular free Ca2+ concentration brought about by cytokinin action.
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    Über Erdalkalimetalloxogallate. VIII Synthese und Aufbau eines neuen Calciumoxogallats: Ca3Ga4O9 (1981)
    Springer
    Monatshefte für Chemie 112 (1981), S. 149-156 
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    ISSN: 1434-4475
    Keywords: Calcium ; Gallium ; Oxygen ; Single Crystal ; X-Ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hitherto unknown compound Ca3Ga4O9 was prepared and investigated by X-ray single crystal methods. Ca3Ga4O9 has orthorhombic symmetry:a=1435.8;b=1682.5;c=532.1 pm; space group C 2v 11 −Cmm2,Z=6. The tetrahedra network (circles of 4 and 5 GaO4-tetrahedra) and the surrounding of Ca2+ are described and discussed with respect to other oxogallates.
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    Effect of dietary cholecalciferol deficiency on plasma thyroid hormone concentrations in rainbow trout,Salmo gairdneri (Pisces, Salmonidae) (1980)
    Springer
    Environmental biology of fishes 5 (1980), S. 167-173 
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    ISSN: 1573-5133
    Keywords: Vitamin D ; Thyroid gland ; Growth ; Endocrines ; Trout ; Calcium ; Thyroxine ; Triiodothyronine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Diets deficient in vitamin D effected a significant increase in plasma triiodothyronine (T3) concentration in raibow trout (Salmo gairdneri); different levels of dietary calcium exerted no effect on plasma T3 levels. These effects of vitamin D deficiency on plasma T3 levels appeared to be reversible, vitamin D supplementation after a period of vitamin D deficiency lowered T3 levels. Vitamin D3, vitamin D2 and the metabolites 25(OH)-D3 and 1, 25(OH)2D3 were all effective in lowering plasma T3 levels; vitamin D3 appeared to be more effective than vitamin D2. There appeared to be a correlation between weight gain and plasma T3 concentration in the groups fed different types and levels of vitamin D supplementation suggesting that the increased T3 levels may be a compensatory increase to the reduced weight gain of the vitamin D deficient fish. Plasma T4 levels were not affected by dietary vitamin D deficiency.
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    Nutrition ofPinus caribaea in its native savanna habitat (1982)
    Springer
    Plant and soil 64 (1982), S. 381-391 
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    ISSN: 1573-5036
    Keywords: Atmosphere ; Calcium ; Fertility ; Forestry ; Magnesium ; Nitrogen ; Nutrients ; Phosphorus ; Pinus caribaea ; Potassium ; Savanna ; Sodium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Fertility levels in soils beneathPinus caribaea trees were examined in the Mountain Pine Ridge savannas, Belize, where fire control has precipitated the development of pine woodland. Slight surface soil enrichment was recorded beneath pine canopies, but to levels well below those found beneath associated hardwoods. Estimates of total nutrient pools beneath trees showed modest cation accumulation beneath a 73 year old tree but some defecits in Ca and Mg beneath a 24 year old tree. A tap root cutting experiment on trees of the same species revealed no significant declines in foliar nutrient levels after 19 months. It is concluded that no pronounced long-term deterioration in soil fertility levels is developing beneath stands ofP. caribaea in the savanna, although some temporary nutrient declines may exist beneath young pine stands. Atmospheric inputs are the most likely source of nutrient accretion and it is suggested that the establishment of hardwood associates with pine may enhance the rates of nutrient capture from this source.
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    Soil amelioration effects on peanut growth, yield and quality (1982)
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    Plant and soil 65 (1982), S. 319-334 
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    ISSN: 1573-5036
    Keywords: Arachis hypogaea L. ; Calcium ; Gypsum ; Lime ; Nodulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In order to study the reasons for poor peanut (Arachis hypogaea L.) performance on an Avalon medium sandy loam, a three year field study was undertaken to investigate the effects of lime and gypsum applications on growth, yield and quality. Rates of up to 2,400 kg agricultural lime/ha/annum significantly increased soil pH (1N KCl) and exch. Ca and decreased levels of exch. Al and Al saturation in the soil (0–150 mm). The effect of the same rates of gypsum was much less marked, only exch. Ca increasing and Al saturation decreasing to any substantial extent. In the absence of lime (i.e. even where gypsum was applied). nodulation was poor and the plants developed a general chlorosisc. 90 days after planting. Liming markedly improved nodulation whereas annual applications of gypsum had the opposite effect. Liming significantly increased the hay, pod and kernel yields by up to 73, 105 and 117%, respectively. On average, gypsum applications had no significant effects. Liming increased shelling percentage, the percentage mature pods, 100-kernel mass and protein concentration in the kernel, and decreased the incidence of pops and kernels with black plumule. Applications of gypsum had little effect on quality except for a decreased incidence of black plumule. It appeared that the improved crop performance with liming resulted from a reduction in Al toxicity which improved nodulation. Calcium deficiency did not appear to be a major cause of poor peanut growth and quality in the unameliorated soil.
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    The effect of calcium on the germination, growth and mineral nutrition of acidic and calcareous populations ofEucalyptus obliqua L'Hérit (1982)
    Springer
    Plant and soil 69 (1982), S. 213-223 
    Details
    ISSN: 1573-5036
    Keywords: Calcareous ; Calcium ; Chlorosis ; Eucalyptus obliqua ; Germination ; Potassium/calcium ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A comparative study of two populations ofE. obliqua has shown that germination of an acidic population is severely reduced at high levels of Ca, whereas a calcareous population maintained high germinability over a wide range of Ca concentrations. In contrast, seedlings of both populations showed a similar overall response in yield to an increasing supply of external Ca. However, plants from the acidic population tended to show a lower survival rate and poorly growing plants accumulated higher levels of Ca and P at high external concentrations of Ca than the calcareous population. Plants showing severe chlorosis and symptoms of P and Ca toxicity also exhibited low K/Ca ratios.
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    Nutrient accumulation byPinus caribaea in its native savanna habitat (1982)
    Springer
    Plant and soil 69 (1982), S. 105-118 
    Details
    ISSN: 1573-5036
    Keywords: Calcium ; Fertility ; Forestry ; Magnesium ; Nitrogen ; Nutrients ; Phosphorus ; Pinus caribaea ; Potassium ; Savanna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Concentrations of P, N, K, Ca, and Mg in above-ground tissues ofP. caribaea were sampled in the species'native savanna habitat. Concentrations were relatively low, but some evidence of higher consumption of K and Ca was found in trees grown on more fertile soils. Regressions were developed to predict the quantities of nutrients sequestered in above-ground tree tissues, and estimates made of the quantities stored in above-ground stands of this species in its native habitat and in several plantations elsewhere. Estimates were also made of the nutrient removals to be expected by harvesting these stands in different ways. Nutrient quantities stored in stands generally exceed those extractable from savanna surface soils, and it is suggested that inputs from the atmosphere are the most probable alternate nutrient source. A comparison of these inputs for tropical areas with the quantities required for stand growth in the savanna, and harvesting removals, suggests that an adequate supply of all elements except P exists, provided that capture by pine is effective. However, atmospheric inputs generally fall below the storage and harvest removal rates for fast growing exotic plantations of this species suggesting that multiple rotations of these plantations at current growth rates may not be feasible without artifical fertilization.
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    Nutrient inflows into apple roots (1983)
    Springer
    Plant and soil 71 (1983), S. 371-380 
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    ISSN: 1573-5036
    Keywords: Apple ; Calcium ; Copper ; Iron ; Irradiance ; Magnesium ; Manganese ; Nitrogen ; Nutrient uptake rate ; Phosphorus ; Potassium ; Scion effects ; Season ; Source of nitrogen ; Temperature ; Tissue nutrient level ; Zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The rates of uptake of nutrients from solution by apple roots were measured (a) in a root laboratory, using intact roots of mature trees growing under field conditions and (b) in controlled environment using young trees. Maximum nitrate inflows into Discovery/M.9 roots under field conditions were only slightly lower than those into roots of the same genotype in controlled environment, but up to 80 times lower than those into roots of Worcester Pearmain seedlings. At any given external P concentration, P inflows into roots of field-grown trees were about 2.5-times lower than those into the roots of young trees in controlled environment. Nitrate inflows were constant above a solution concentration of 20 mmol m−3 in both field-grown and small trees. In both cases, phosphate inflows increased linearly with solution concentration up to 10 mmol m−3. Among the various plant and environmental factors influencing nutrient uptake characteristics of apple roots were: the scion genotype, tissue nutrient levels, root origin, the form in which N is supplied, level of irradiance of the shoot, root temperature and the season of the year. The effects of these factors are illustrated with examples.
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    Soil organic matter and structural stability: mechanisms and implications for management (1984)
    Springer
    Plant and soil 76 (1984), S. 319-337 
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    ISSN: 1573-5036
    Keywords: Aggregates ; Aluminium ; Bacterial mucilage ; Binding agents ; Calcium ; Cation bridges ; Complexing agents ; Dispersion ; Electron microscopy ; Electrophoretic mobility ; Fungal hyphae ; Glues Iron ; Management Periodate ; Polysaccharides ; Rhizosphere ; Roots ; Slaking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The stability of pores and particles is essential for optimum growth of plants. Two categories of aggregates macro- (〉 250 μm) and micro- (〈250 μm) depend on organic matter for stability against disruptive forces caused by rapid wetting. Dispersion of clay particles from microaggregates is promoted by adsorption of complexing organic acids which increase the negative charge on clays. The acids are produced by plants, bacteria and fungi. However, the dispersibility of clay in microaggregates is offset by the binding action of polysaccharides, mainly mucilages produced by bacteria, but also by plant roots and fungal hyphae. The stability of microaggregates is also enhanced by multivalent cations which act as bridges between organic colloids and clays. Macroaggregates are enmeshed by plant roots, both living and decomposing, and are thus sensitive to management, and increase in number when grasses are grown and the soil is not disturbed. Lack of root growth,i.e. fallow, has the opposite effect. Various implications for management of soil structure are discussed.
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    Aluminium effects on growth and Al, Ca, Mg, K and P levels in triticale, wheat and rye (1980)
    Springer
    Plant and soil 57 (1980), S. 467-470 
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    ISSN: 1573-5036
    Keywords: Aluminum concentration ; Aluminum toxicity ; Calcium ; Magnesium ; Nutrient solution ; Phosphorus ; Potassium ; Triticale ; Rye ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of A1 on the growth and mineral composition of different cultivars of triticale (X Triticosecale, Wittmack), wheat (Triticum aestivum L.) and rye (Secale cereale L.) growing in 1/5 strength Steinberg solutions containing 0 or 6 ppm A1 were evaluated after 32 days. Aluminum increased the concentrations of P and K in the roots and K in the tops of most of the cultivars tested. A1 tolerant triticale retained a lower concentration of Mg in the roots and tops than the A1 sensitive triticale, when subjected to A1 stress. In addition, A1 treatments resulted in smaller increases in root P for the A1 tolerant triticale than for the A1 sensitive cultivars. The concentration of root Ca and P of the A1 tolerant wheat cultivars were significantly below that of the more sensitive plants. Aluminum tolerance in rye appeared to be associated with lower Ca and higher Mg concentrations in the tops. The accumulation of P and A1 in the roots was characteristic of sensitivity in triticale, wheat and rye.
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    Soil acidity factors and nodulation ofTrifolium repens (1984)
    Springer
    Plant and soil 78 (1984), S. 367-379 
    Details
    ISSN: 1573-5036
    Keywords: Acidity ; Aluminium ; Calcium ; Manganese ; Nodulation ; pH Rhizobium ; Rhizosphere ; Root elongation ; Root hairs ; Trifolium repens ; White clover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Effects of factors associated with soil acidity (low pH, low calcium, high aluminium and high manganese) on theTrifolium repens-Rhizobium trifolii symbiosis were investigted under laboratory conditions using an axenic solution-culture technique. 200 μM manganese increased root elongation in the range pH 4.3–5.5, but had no effect on root hair formation, the number of Rhizobium in the rhizosphere, or nodule formation. Root elongation and root hair formation were unaffected at pH 4.3 when 500 or 1000μM calcium was supplied, whereas multiplication of Rhizobium in the rhizosphere and nodulation were inhibited at pH 4.3 and 4.7.50–1000μM calcium had no effect either on the multiplication of Rhizobium in the range pH 4.3–5.5, or on nodule formation in the absence of aluminium. 50 μM aluminium inhibited, root elongation and root hair formation at pH 4.3 and 4.7; the effect on root elongation was reduced by increasing the calcium concentration from 50 to 1000μM. 50μM aluminium also inhibited Rhizobium multiplication in the rhizosphere and reduced nodule formation at pH 5.5 (at which aluminium precipitated out of solution), but root elongation and root hair formation were unaffected. These, effects of aluminium at pH 5.5 may explain the poor response to inoculation by white clover in acid mineral soils after liming.
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    Ionic interactions in rice plants from dilute solutions (1983)
    Springer
    Plant and soil 70 (1983), S. 309-316 
    Details
    ISSN: 1573-5036
    Keywords: Calcium ; Ionic interaction ; Magnesium ; Nutrient solution ; Oryza sativa L. ; Phosphorus ; Potassium ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Ionic interactions may occur as cation-cation interactions, anion-anion interactions, or cation-anion interactions. Greater knowledge of this subject is warranted, due to the intensification of agriculture, in devising efficient fertilization systems. The present study was undertaken to elucidate the interaction among P, K, Ca and Mg absorption by the intact rice (Oryza sativa L.) plants from dilute solutions. The uptake of P was independent of Ca concentrations up-to 250 μM Ca but-there was a small decrease at the higher concentrations. Absorption of K and Mg was stimulated in the presence of Ca ions at low concentrations. But K and Mg absorption was decreased at higher Ca concentrations. Increasing concentrations of K in the nutrient solution depressed P and Ca uptake. Magnesium uptake was stimulated at lower concentrations of K, but at higher concentrations it was also decreased. Similarly, absorption of K and Ca was also decreased with increasing concentrations of Mg. Magnesium at lower concentrations stimulated P uptake but at higher concentraions it was decreased. In the present study maximum growth of rice plants was achieved at about 250μM Ca, 260 μM K, and 33μM Mg in the nutrient solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02374887
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    Plant genotype differences in the uptake, translocation, accumulation, and use of mineral elements required for plant growth (1983)
    Springer
    Plant and soil 72 (1983), S. 175-196 
    Details
    ISSN: 1573-5036
    Keywords: Boron ; Calcium ; Copper ; Genotypic differences ; Iron ; Magnesium ; Manganese ; Mineral nutrition ; Molybdenum ; Nitrogen ; Phosphorus ; Plant adaptation ; Plant breeding ; Potassium ; Zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plant genotypes differ in their uptake, translocation, accumulation, and use of mineral elements. Examples of genotype differences to iron, nitrogen, phosphorus, potassium, calcium, magnesium, manganese, boron, copper, zinc, and molybdenum are discussed. Current knowledge is sufficient to indicate that many crop plants can be improved for the efficient use of mineral elements and better adaptation to mineral stress conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02181957
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    The search for and interpretation of genetic controls that enhance plant growth under deficiency levels of a macronutrient (1983)
    Springer
    Plant and soil 72 (1983), S. 335-350 
    Details
    ISSN: 1573-5036
    Keywords: Calcium ; Nutrient stress ; Phosphorus ; Potassium ; Root growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Techniques developed to measure growth of tomatoes and beans under limiting amounts of either P, K or Ca in solution culture reveal differences among strains. Genetic analysis permits estimates of gene action for control of efficiency and the isolation of improved segregants. The genetic isolates have value in studying mechanisms contributing to uptake, transport and utilization processes.
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    URL: http://dx.doi.org/10.1007/BF02181972
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    Association of cation and organic anion accumulation with iron chlorosis of Scots pine on prairie soils (1980)
    Springer
    Plant and soil 56 (1980), S. 293-300 
    Details
    ISSN: 1573-5036
    Keywords: Calcareous soils ; Calcium ; Cation-anion balance ; Induced-iron chlorosis ; Nitrate ; Organic anions ; Pinus sylvestris L ; Prairie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Iron chlorosis of 4 year old Scots pine (Pinus sylvestris L.) in comparison to areas of adjacent healthy growth on calcareous prairie soil, was associated with slight increases in the soluble ion content of the saturation paste extract. Such increases in soluble ions (mainly calcium sulphate) were associated with significant increases in ash, cation (including iron) and organic anion content of the chlorotic needles. Increasing levels of available soil nitrate were also related to increase in organic anions. Nitrogen and phosphorus assimilation was adversely affected under conditions of iron chlorosis. These observations support the theory of induced iron deficiency associated with elevated levels of organic anions or translocated cations and are applicable to plantings of conifers on prairie soils.
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    URL: http://dx.doi.org/10.1007/BF02205858
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    Effects of artificial acid rain on decomposition of spruce needles and on mobilisation and leaching of elements (1980)
    Springer
    Plant and soil 56 (1980), S. 365-378 
    Details
    ISSN: 1573-5036
    Keywords: Acid rain ; Calcium ; Decomposition ; Leaching ; Magnesium ; Manganese ; Mobilisation ; Nitrogen ; Phosphorus ; Potassium ; Spruce litter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Dry matter and chemical changes in decomposing spruce needles were investigated after 16 and 38 weeks in laboratory lysimeters treated with distilled water or distilled water acidified to pH 3 or 2 with sulphuric acid. The water was added twice weekly in quantities equal to 100 or 200 mm month−1. The CO2 evolution and leaching of P, K, Mg, Mn, and Ca was followed together with pH measurements of the leachate. The loss of dry matter was approximately 25% during the first 16 weeks and approximately 37% after 38 weeks. At the first samling, 16 weeks, the amount of material decomposed was greater from the lysimeters given 100 mm month−1 of water. At this water quantity dilute sulphuric acid increased the decomposition. After 38 weeks sulphuric acid at pH 3 and 2 had decreased the decomposition at 200 mm month−1. However, the effects of acid application were small. The effect of treatment using acidified water on the content of monosaccharides was not consistent, whereas there was an indication of reduced decomposition of lignin when treated with 200 mm water month−1 at pH 3 and 2. Nitrogen was conserved in the lysimeters with small differences between the various treatments. The order of mobility of metal elements was K〉Mg〉Mn〉Ca. Increasing the quantity of water increased the leaching of K especially, whereas addition of dilute sulphuric acid increased the leaching of Mg, Mn and particularly Ca. During the first 16 weeks of the experiment, sulphuric acid reduced the leaching of P while later on this treatment increased the leaching. The pH of the leachate from the lysimeters treated with distilled water was initially 4.0–4.6 increasing to approximately 6.6 after 22 weeks. The pH of the decomposed needle material was 4.6 and approximately 5.2 after 16 and 38 weeks respectively. When treated with water at pH 3 the pH of the leachate was between 4 and 5, and the pH of the needles 4.2–5.1. Treatment with water at pH 2 gave a leachate with pH just above 2 and decreased the pH of the needles that had received 200 mm ‘rain’ month−1 to 2.9. The effect of the artificial acid rain appears to be more pronounced on the leaching of metal elements than on the biological activity and the dynamics of N and P. The treatments must be considered extreme when compared with the acidity of natural rain.
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    URL: http://dx.doi.org/10.1007/BF02143031
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    Relationships of bio-climatic zones and lithology with various characteristics of forest soils in Greece (1984)
    Springer
    Plant and soil 79 (1984), S. 101-121 
    Details
    ISSN: 1573-5036
    Keywords: Base saturation ; Bio-climatic zones ; Calcium ; Clay accumulation ; Copper ; C:N ratio ; EDTA ; Forest soils ; Greece ; Iron ; Magnesium ; Manganese ; Nitrogen ; Phosphate ; Potassium ; Soil classification ; Zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soils derived from a number of different parent materials (lithologies) and developed along a climatic gradient, manifested by the altitudinal succession of natural vegetation zones (Mediterranean, sub-Mediterranean, Mountainous and Pseudoalpine), were sampled throughout mainland Greece. In soils derived from siliceous parent materials low in clay, acidity increase and percent base saturation decreases from the Mediterranean to the Pseudoalpine vegetation zones. Clay illuviation is found mainly in soils developed in the Mediterranean and the sub-Mediterranean zones. No such changes are apparent in clayey soils rich in bases. Organic matter content of the mineral portion of the soil profile increases by a factor of 2 with a decrease in mean annual air temperature of about 10°C. The pattern of change in clay and soil organic matter content with climate is in relatively good agreement with soil development trends in the area, when soil profiles are named according to the FAO-Unesco soil map of the world. Concentrations of Ca and Mg decrease and those of total N, total and extractable P, K, Fe, Mn and Zn increase from the Mediterranean to the Mountainous zone. Within the same zone, however, concentrations of N, Ca, K, Fe, Mn and Zn decrease, but those of Mg, total and extractable P increase with soil depth. The concentrations of most macro- and micronutrients in the humic horizon are several times higher than those in the mineral portion of the soil profile due to biological enrichment.
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    URL: http://dx.doi.org/10.1007/BF02182148
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    Effects of waterlogging on young wheat plants (Triticum aestivum L.) and on soil solutes at different soil temperatures (1982)
    Springer
    Plant and soil 69 (1982), S. 311-326 
    Details
    ISSN: 1573-5036
    Keywords: Aeration ; Calcium ; Carbon dioxide ; Ethylene ; Nitrate ; Nitrite ; Nitrous oxide ; Oxygen ; Potassium ; Roots ; Triticum aestivum ; Waterlogging ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We report a study of the mechanism by which the response of plants to waterlogging can be modified by soil temperature. Wheat was grown initially in well-aerated soil in a controlled environment room before the soil was flooded with aerated, deionized water. The soil temperature was maintained constant in the range 6–18°C while the air temperature was at 14°C. Waterlogging damage was greater in plants at the higher soil temperatures when the plants were compared at the same chronological age. However, when compared at the same growth stage, the response to soil temperature was little differenti.e. plants subjected to waterlogging for a long time at low soil temperatures exhibited a similar reduction in growth and other properties as those subjected briefly at higher temperatures. The concentration of dissolved oxygen in the soil solution declined rapidly at all temperatures, being almost zero after 36 h waterlogging. Temperature affected rates of change of the concentrations of dissolved carbon dioxide, ethylene, nitrous oxide, nitrite, nitrate, calcium and potassium. The importance of soil-and plant-determined properties in the waterlogging response of plants at different temperatures are discussed.
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    URL: http://dx.doi.org/10.1007/BF02372453
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    Studies on the possible role of cation exchange capacity in the soil preference of mosses (1983)
    Springer
    Plant and soil 70 (1983), S. 77-93 
    Details
    ISSN: 1573-5036
    Keywords: Adsorption ; Calcium ; Calcium carbonate ; Cation Exchange Capacity ; Hydrogen ; Magnesium ; Moss ; pH ; Potassium ; Sodium ; Soil preference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Moss species with a different soil preference with respect to its acidity and carbonate content also differ in their cation exchange capacity (leaf, stem, rhizoid), the acidiphile-calcifuges having lower C.E.C. values than the neutrophile-calcicoles. The higher the C.E.C. value, the more the divalent cations calcium and magnesium tend to be adsorbed as compared to the monovalents sodium and potassium, from an equinormal tetracationic solution. The increase in divalent adsorption is mainly due to calcium. Considering this differential adsorption of calcium and in view of data in literature on membrane characteristics, it appears that among the studied cations calcium is an important factor in the observed soil preference through its presence in the cell wall adsorbed fraction and thus in the membrane environment.
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    URL: http://dx.doi.org/10.1007/BF02374752
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    Taxonomic character of plant species in absorbing and accumulating alkali and alkaline earth metals grown in temperate forest of Japan (1983)
    Springer
    Plant and soil 70 (1983), S. 367-389 
    Details
    ISSN: 1573-5036
    Keywords: Alkali metals ; Alkaline earth metals ; Barium ; Calcium ; Ceasium ; Lithium ; Magnesium ; Potassium ; Rubidium ; Sodium ; Strontium ; Temperate forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Absorption and accumulation of alkali (Li, Na, K, Rb, Cs) and alkaline earth (Mg, Ca, Sr, Ba) metals were investigated as taxonomic characteristics (in 62 plant species). Leaf and soil samples were collected from 9 sites in temperature forest in Japan and the above mentioned elements were analyzed. Considerable differences were found among species in their ability to accumulate alkali and alkaline earth metals. Very high concentrations of Li (45 ppm, D.W.), K (37×103 ppm), Rb (159 ppm) and Cs (8.2 ppm) were detected inLastrea japonica which were about 412, 12, 27 and 6 times higher than those of the species with the lowest concentrations. Na content was high inAcer micranthum (358 ppm) which was 16 times higher than species with the lowest concentration. Other species containing high levels of alkali metals wereHydrangea macrophylla, Struthiopteris niponica, Clethra barbinervis. Mean discrimination ratio (D.R.) for all investigated plant species for Li, Na, Rb, and Cs to K were 1.7, 0.44, 0.9 and 1.8 respectively. High concentrations of alkaline earth metals Ca (36×103 ppm), Sr (345 ppm), and Ba (241 ppm) were found in the leaves ofHydrangea paniculata which were about 31, 84, and 72 times higher than those for the species with the lowest concentration. Mg was very high inStruthiopteris niponica (83×102 ppm). Other species with high concentrations of alkaline earth metals belonged to the genus Viburnum. Mean D.Rs. for Mg, Sr, and Bavs Ca were 1.0, 0.7 and 0.08. Principal component analysis of interrelationships between the mineral content in leaf tissues indicated that these elements could be classified into 2 groups with respect to their accumulation behavior in plants. The alkali metals K, Li, Rb, and Cs behaved similarly in their accumulation in leaves but Na behaved independently. Alkaline earth metals Ca, Mg, Sr, and Ba were also found to behave similarly in their accumulation. Factors scores of 1st and 2nd components revealed three groups of plant species: alkaliphilic, alkaline earthphilic, and neutral (non-accumulators).
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    URL: http://dx.doi.org/10.1007/BF02374893
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    Nutritional differentiation within the speciesDittrichia viscosa W. Greuter, between a population from a calcareous habitat and another from an acidic habitat (1983)
    Springer
    Plant and soil 72 (1983), S. 297-303 
    Details
    ISSN: 1573-5036
    Keywords: Calcicole ; Calcifuge ; Calcium ; Dittrichia viscosa ; Magnesium ; Potassium ; Sodium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Dittrichia viscosa is a Mediterranean bush widespread on various soil types. It is shown that the plants from a calcareous habitat (G plants) and those from an acidic habitat (M plants) differ in their ability to accumulate various cations when growing in the same experimental conditions. On this acidic soil the G plants accumulate more Ca and less K than the M plants. On a calcareous soil the response is reversed; it is the M plants which contain more Ca and often less K. This behaviour on each of the soils is typically that of a calcifuge for M and a calcicole for G. The two types of plants also differ in their affinity for Mg and Na. The ubiquity of the species could well be explained at least partially by genetic differentiation in the ability of plants to select ions.
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    Foliar and twig macronutrients (N, P, K, Ca and Mg) in selected species ofEucalyptus used in rehabilitation: sources of variation (1984)
    Springer
    Plant and soil 81 (1984), S. 363-376 
    Details
    ISSN: 1573-5036
    Keywords: Branch nutrients ; Calcium ; Eucalyptus saligna ; Eucalyptus wandoo ; Foliar nutrients ; Magnesium ; Nitrogen ; Phosphorus ; Potassium ; Rehabilitation ; Soil nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The macronutrient variation within four 6 year oldEucalyptus saligna and four 5 year oldE. wandoo growing on rehabilitated bauxite pits was determined. Significant differences in mean nutrient concentrations were generally recorded between good soil condition sites and poor soil sites, between tree individuals, branch height, and plant organ type; but mean nutrient values were not different among canopy aspects. Fully expanded leaves of the current year provided the most uniform nutrient levels among the plant organs and showed major differences between sites with good soil nutrient conditions and those with poor conditions. Differences in foliar and branch levels of N, P, K, Ca and Mg, the variation between sites, canopy heights and plant organ types, and the use of foliar nutrient levels to indicate deficiencies are discussed.
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    URL: http://dx.doi.org/10.1007/BF02323051
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    Seasonal changes in foliar macronutrients (N, P, K, Ca and Mg) inEucalyptus saligna Sm. andE. wandoo Blakely growing in rehabilitated bauxite mine soils of the Darling Range, Western Australia (1984)
    Springer
    Plant and soil 81 (1984), S. 377-388 
    Details
    ISSN: 1573-5036
    Keywords: Calcium ; Eucalyptus saligna ; Eucalyptus wandoo ; Foliar nutrients ; Magnesium ; Nitrogen ; Phosphorus ; Potassium ; Rehabilitation ; Seasonal trends
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Seasonal changes in the foliar concentration of macronutrients (N, P, K, Ca and Mg) in sapling trees ofEucalyptus saligna Sm. andE. wandoo Blakely growing in rehabilitated bauxite mined areas in the Darling Range of Western Australia are described. Foliar N concentration decreased with age of the fully expanded leaf tissue. Leaf N concentrations were also high when rates of litter decomposition were expected to be high during the period of early spring. The greatest foliar N difference between trees growing in good soil conditions and those from poorer soil conditions also occurred during this period. Levels of P in leaves were highest in young developing leaves but once the leaves reached full size, no seasonal trend in P concentration was observed. Foliar K was lower during the winter and probably related to the period of maximum leaching by precipitation. High foliar K during summer, however, could be related to the role of K in lowering cellular water potential. Leaf Ca was highest during early sping. Low mobility of cellular Ca during the cool portion of the year was indicated. Foliar Mg showed a weak pattern of decreasing concentration with leaf age. The best season for sampling for these broadleafed evergreen species to provide information on plant nutrient status appears to be in spring.
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    Vesicular-arbuscular mycorrhizal infection in lettuce (Lactuca sativa) in relation to calcium supply (1984)
    Springer
    Plant and soil 82 (1984), S. 61-67 
    Details
    ISSN: 1573-5036
    Keywords: Calcium ; Glomus caledonium ; Glomus mosseae ; Lactuca sativa ; Vesicular-arbuscular mycorrhiza
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Infection of lettuce roots (Lactuca sativa L.) by the vesicular-arbuscular mycorrhizal fungiGlomus caledonium andGlomus mosseae was dependent on the amount of calcium (supplied as CaCl2·2H2O or CaSO4·2H2O) in the nutrient solution; those plants growing at low calcium concentrations being poorly infected.
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    URL: http://dx.doi.org/10.1007/BF02220770
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    Stabilité biologique et comportement physique d'un complexe argilo-humique placé dans différentes conditions de saturation en calcium ou en potassium (1984)
    Springer
    Plant and soil 77 (1984), S. 271-284 
    Details
    ISSN: 1573-5036
    Keywords: Calcium ; Cation de liaison ; Complexes organo-minéraux ; Minéralisation ; Stabilisation de la matière organique ; Structure ; Calcium ; Cation bridge ; Fixation of organic matter ; Mineralisation ; Organomineral compounds ; Structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary By gradually removing the exchangeable calcium held by the organo-mineral complex of an organic soil from the Jura mountains, the authors showed: a direct action of the microflora on the mineralisation of organic matter (Fig. 7) and on the generation of mineral nitrogen (Fig. 3); an indirect action by the mineralisation of organic matter on the destabilisation of the clay-humus complex. They therefore concluded that the reduction of calcium resulted in the destabilisation of the organo-mineral complex by H+, produced by the biodegradation of the most labile portion of the organic matter. The clay humus complex gradually dissociated. This process lead to the destruction of aggregates and organo-mineral complexes. The organic matter released became biodegradable due to the shortage of calcium.
    Notes: Résumé Les auteurs sont partis d'un complexe organo-minéral calcique provenant d'un sol humifère du Jura et ont provoqué une diminution progressive au cours du temps du taux de calcium échangeable. L'étude de l'évolution de divers paramètres, menée parallèlement, a permis d'analyser les effets directs et indirects de la baisse du calcium sur le complexe organo-minéral. Les résultats obtenus concernent: 1. les effets directs de l'action minéralisatrice de la microflore sur la dégradation de la matière organique (Fig. 7) et la production d'azote minéral (Fig. 3). 2. les effets indirects de cette minéralisation sur la déstabilisation du complexe argilo-humique (Fig. 8). Ils permettent d'affirmer qu'un complexe organo-minéral calcique évolue très rapidement quand l'apport d'ions calcium vient à diminuer ou à être supprimé. Les ions Ca2+ sont très vite déplacés et remplacés par des ions H+ produits par la biodégradation des fractions les plus labiles de la matière organique. Le complexe argile-calcium-humus est progressivement dissocié. Le processus conduit à une destruction des agrégats avec libération des argiles et de la matière organique qui devient à son tour biodégradable. l'effet stabilisateur du calcium ayant disparu.
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    pH optima for crop growth (1980)
    Springer
    Plant and soil 54 (1980), S. 339-357 
    Details
    ISSN: 1573-5036
    Keywords: Calcium ; Cassava ; Chemical composition ; Control of solution pH ; Copper ; Flowing solution culture ; French bean ; Ginger ; Hydrogen ion injury ; Magnesium ; Maize ; Manganese ; Nitrogen ; Optimum pH range ; pH ; Plant growth ; Root weight ratio ; Tomato ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Ginger, cassava, maize, wheat, french bean and tomato were grown for periods up to six weeks in continuously flowing nutrient solutions at seven constant pH values ranging from 3.3 to 8.5. All species achieved maximum or near-maximum growth in the pH range 5.5 to 6.5. However, there were substantial differences in the ability of species to grow outside this range. Ginger and cassava were the most tolerant species to low solution pH, while ginger and tomato were the only species to show no yield depression at the highest solution pH. Roots of all species at pH 3.3 and some species at pH 4.0 exhibited symptoms of hydrogen ion injury. In addition, the concentrations of magnesium in the tops of all six species, of nitrogen in the tops of tomato and cassava, and of manganese in the tops of maize at these pH values were inadequate for optimal growth. Growth depression at high solution pH was associated with iron deficiency in maize and wheat and with nitrogen and/or copper deficiency in cassava. The relevance of the present results to crop growth under field conditions is discussed. The complex interplay of plant and soil characteristics militates against precise definition of an optimum pH range for the growth of a particular crop unless the soil is also specified.
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    Effects of a soil fulvic acid on the growth and nutrient content of cucumber (Cucumis sativus) plants (1981)
    Springer
    Plant and soil 63 (1981), S. 491-495 
    Details
    ISSN: 1573-5036
    Keywords: Calcium ; Copper ; Flowers ; Iron ; Leaves ; Magnesium ; Nitrogen ; Nutrient uptake ; Phosphorus ; Potassium ; Koots ; Shoots ; Zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Cucumber (Cucumis sativus) plants were grown in Hoagland solution to which 20 to 2000 ppm of a soil fulvic acid (FA) were added. The addition of 100 to 300 ppm of FA produced highly significant increases in the growth and development of above and below ground plant parts, in the uptake of nutrient elements (N, P, K, Ca, Mg, Cu, Fe and Zn), and in the formation of numbers of flowers per plant. Effects of adding 500 and more ppm of FA were less beneficial.
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    URL: http://dx.doi.org/10.1007/BF02370049
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    Effects of dry and moist incubation of soils on the extractability of native and applied soil copper (1982)
    Springer
    Plant and soil 64 (1982), S. 215-224 
    Details
    ISSN: 1573-5036
    Keywords: Calcium ; chloride-extractable Cu ; Copper ; EDTA-extractable Cu ; Incubation ; Isotopically-exchangeable Cu ; Moisture content ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The amount of copper extracted from soils by EDTA was found to increase with the temperature of extraction. Under controlled conditions of extraction, the amount of applied copper extracted from soils by EDTA decreased during incubation of soils under both moist and dry conditions. The recovery of applied copper by EDTA appeared to be related to the amounts of manganese and iron oxides in the soil. On the basis of comparisons with calcium chloride-extractable copper and isotopically-exchangeable copper it is suggested that EDTA extraction could over-estimate the availability of soil copper to plants.
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    URL: http://dx.doi.org/10.1007/BF02184253
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    Effects of acid irrigation and liming on two clones of Norway spruce (1980)
    Springer
    Plant and soil 57 (1980), S. 305-321 
    Details
    ISSN: 1573-5036
    Keywords: Aluminium ; Acid precipitation ; Calcium ; Calcium carbonate ; Clone ; Iron ; Magnesium ; Manganese ; Nitrogen ; Picea abies ; Phosphorus ; Potassium ; Sulphate ; Sulphur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of acid irrigation on the growth of rooted cuttings ofPicea abies (L.) Karst, was investigated in a pot experiment lasting 3 years. It involved two clones of Norway spruce, H 253 Bogstad I and H 254 Bogstad II. Irrigation water of pH 5.4, 4.0, 3.0 and 2.5 was used. Liming was included in the experiment. After the experimental period, the plants of all treatments were growing reasonably well. However, those plants irrigated at pH 2.5 were slightly discoloured. The plant mortality was only 3% throughout the experiment, and was not connected to acid irrigation. The limiting growth factor was N. All other nutrient elements measured in the plants were close to optimal concentration. Plants irrigated at pH 2.5, and to some extent at pH 3, contained excessively high concentrations of Al, t-S and SO4. The total amount of Ca, Fe and Mn taken up by the plants decreased with increasing soil acidity. The increased growth of clone H 254 relative to H 253, produces a corresponding impression on soil characteristics. Soil acidity is governed by acid irrigation and CaCO3 application, but the clonal effects are also of importance. Norway spruce appears to be tolerant to Al concentrations as high as 50 mmol/kg in the needles.
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    Adsorption and exchange of Ca, Mg and K-ions on the root cell walls of clover and rye-grass (1984)
    Springer
    Plant and soil 80 (1984), S. 181-190 
    Details
    ISSN: 1573-5036
    Keywords: Adsorption ; Calcium ; CEC ; Cell wall ; Clover ; Exchange ; Magnesium ; Model ; Potassium ; pH ; Root ; Rye-grass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The ion exchange properties of clover and rye-grass root cell walls were studied quantitatively. Three sets of experiments were performed: adsorption of Ca, Mg and K ions versus pH, adsorption versus cation concentration and exchange isotherms Ca−Mg and Mg−K. A model has been developed. It allows the satisfactory prediction of results (except for pH curves) with the adjustment of a minimum of parameters. The total charge (RT), on its own, accounts for the difference between the ion exchange properties of the clover and rye grass cell walls. The selectivities observed on root material are very different from those observed on soil exchange complexes. The decreasing affinities of cell walls for cations follow the sequence: Ca〉Mg≫K for cell walls. These differences of selectivity are much larger than those usually observed for soil exchange complexes.
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    URL: http://dx.doi.org/10.1007/BF02161174
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    Aluminium toxicity expression nutrient uptake, growth and root morphology ofTrifolium repens L. cv. ‘Grasslands Huia’ (1984)
    Springer
    Plant and soil 82 (1984), S. 101-116 
    Details
    ISSN: 1573-5036
    Keywords: Aluminium toxicity ; Calcium ; Phosphate ; Trifolium ; Uptake ; Nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Hydroponic experiments were undertaken to examine the effect of increasing aluminium levels on the mineral nutrition and root morphology ofT. repens growing in nutrient solution. Toxicity symptoms appear between 27.8 and 47.5 μM Al3+ activity (148 to 297 μM total aluminium). The threshold level corresponding to a 10% reduction in leaf fresh weight is estimated to be approximately 20 μM Al3+ activity. The concentration of aluminium in the leaves of white clover increases exponentially with aluminium activity in the nutrient solution. The uptake of divalent cations was inhibited but aluminium enhanced potassium and nitrogen concentrations in both leaves and roots. At high pH (pH 6.0) the speciation of aluminium is controlled by the formation of solid aluminium phosphate and aluminium hydroxide except at the lowest aluminium level (37 μM) where 99.9 per cent is present as the DTPA complex. As the concentration of total aluminium increases, the percentage of Al-DTPA and soluble aluminium hydroxide decreases whilst solid Al(OH)3 increases rapidly to reach a maximum of 91.6 percent (of the total aluminium) in the 1180 μM aluminium treatment. At pH 4.5 the dominant forms of aluminium are free aluminium ion Al-DTPA, AlSO 4 + and AlOH2+. The roots of aluminium stressed plants showed symptoms typical of aluminium toxicity.
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    URL: http://dx.doi.org/10.1007/BF02220774
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    Elemental concentrations in plant tissues as influenced by low pH soils (1980)
    Springer
    Plant and soil 55 (1980), S. 157-161 
    Details
    ISSN: 1573-5036
    Keywords: Acid mine drainage ; Aluminum ; Betula nigra ; Calcium ; Magnesium ; Manganese ; Plant tissue analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soils influenced by acid mine drainage (pH〈5.0) are characterized by low concentrations of essential nutrients and increased solubility of heavy metals. The conditions typically reduce plant establishment and growth. However, river birch (Betula nigra L.) is commonly found along low pH streams in southeastern Ohio. The objective of this study was to determine the concentration of Al, Mn, Ca and Mg inB. nigra tissues. The results indicate Al and Mn are accumulating inB. nigra when compared to other species. Within river birch, Al concentrations are highest in roots; Mn concentrations are highest in leaves. There is not a concomitant reduction in Ca and Mg concentrations as suggested by soil levels.
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    URL: http://dx.doi.org/10.1007/BF02149720
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    Gains and losses in soil nutrients associated with harvesting and burning eucalypt rainforest (1983)
    Springer
    Plant and soil 74 (1983), S. 437-450 
    Details
    ISSN: 1573-5036
    Keywords: Burning controlled ; Calcium ; Carbon ; CEC ; Eucalyptus ; Magnesium ; Nitrogen ; N. mineralisation ; Potassium ; Rainforest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In mixed eucalypt/rainforest in southern Tasmania, samples of surface soil 0 to 2 cm, 2 to 5 cm, and 5 to 10 cm were taken from a clear-felled coupe before and after burning in 1982, from a similar coupe after burning in 1979, and from an uncut area adjacent to each coupe. Factors compared were bulk density; total organic C, N, P, Ca, Mg, and K; pH; exchangeable Ca, Mg, and K; cation exchange capacity; extractable P; and N-mineralisation rates. The effect of burning was found to be restricted mainly to the upper 2 cm of soil. The combustion of organic matter caused losses of 7360 kg organic C and 211 kg N/ha; 348 kg Ca and 282 kg Mg and 151 kg K/ha were added to the soil in ash. Burning caused significant increases in pH, exchangeable Ca, Mg, and K, and in extractable P; cation exchange capacity was reduced. In the 6 months after burning only K was leached from the upper 2 cm of soil. Equilibrium levels of NH4−N increased initially after the fire, but between 6 and 18 months, equilibrium levels and rate of production of NH4−N during anaerobic incubation in soil of burned coupes differed little from that in adjacent uncut forest. Rates of production of NO3−N during aerobic incubation were very low throughout the period of study. It is concluded that for soils developed on dolerite in mixed eucalypt/rainforest, a single regeneration burn probably improves the nutritional status of the soil. Nutrients lost from the area as particulate ash are in quantities that will probably be replaced in rainfall in 15 to 20 years.
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    URL: http://dx.doi.org/10.1007/BF02181361
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    Mechanism of chloroplast movement inMougeotia (1981)
    Springer
    Protoplasma 109 (1981), S. 169-185 
    Details
    ISSN: 1615-6102
    Keywords: Actomyosin ; Anchorage sites ; Calcium ; Chloroplast movement ; Mougeotia sp. ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The single, ribbon-shaped chloroplast in the filamentous green algaMougeotia performs orientational movements with respect to light. The chain of reaction involves phytochrome as the photoreceptor pigment to perceive the light signal differentiated by wavelength and direction, calcium probably to convert the light signal into a chemical message and actomyosin to respond to this message and to move the chloroplast accordingly.Precise reorientation of the chloroplast is proposed to be brought about by a dual function of phytochrome: regulation of the cellular level of calciumand regulation of membrane anchorage sites to actin.
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    Membrane-associated calcium during pollen grain germination: a microfluorometric analysis (1983)
    Springer
    Protoplasma 117 (1983), S. 226-232 
    Details
    ISSN: 1615-6102
    Keywords: Calcium ; Calmodulin ; Chlorotetracycline ; Microfluorometry ; Phenothiazine ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pear (Pyrus communis L.) pollen was germinated and grown in hanging drop cultures containing phenothiazine drugs, trifluoperazine and chlorpromazine, potent inhibitors of the Ca2+-calmodulin complex. Responses for the two drugs were similar: at 1.0–2 10.0 ΜM pollen germination and tube growth were inhibited. Inhibition of tube growth was not uniform; at 10.0 ΜM growth of about half of those tubes which had germinated was inhibited while the remaining half of the population grew normally. This bimodal distribution of tube growth was noted, but to a lesser extent, at lower concentrations of the drugs as well. Microfluorometric analysis of membrane calcium using chlorotetracycline, a fluorescent chelate probe for membrane calcium, revealed that upon pollen grain hydration there was a sharp decrease in the concentration of calcium associated with membranes and that membrane calcium became localized primarily at the periphery of the newly hydrated pollen grain. Prior to germination there was a reloading of calcium onto membranes in the region of the germination aperture through which the pollen tube would emerge. The release of Ca2+ from membrane sites upon hydration was partially inhibited by treatment with 10 ΜM trifluoperazine. Distribution of membrane calcium in populations of the inhibitor-treated pollen grains was not bimodal however; approximately half of the population had CTC-fluorescence emissions exceeding the maximum value found in the control population. These results suggest that there is a maximum concentration of membrane-associated calcium consistent with normal pollen germination and tube growth and that phenothiazines interfere with the unloading of Ca2+ from membrane sites.
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    URL: http://dx.doi.org/10.1007/BF01281826
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    Effect of divalent cations on flagellar scales in the green flagellateTetraselmis cordiformis (1982)
    Springer
    Protoplasma 111 (1982), S. 221-233 
    Details
    ISSN: 1615-6102
    Keywords: Calcium ; Flagellar scales ; Green algae ; Scale topography ; Tetraselmis cordiformis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The structure and topography of flagellar scales (underlayer scales, rodshaped scales, hair-scales) in the green flagellateTetraselmis cordiformis has been studied in detail and the effect of divalent cations and fixation conditions on scale structure and topography was followed quantitatively. Hair-scales occur in two rows on opposite sides of a flagellum and are linked to the flagellar membrane and to two axonemal doublets by B-tubule-flagellar membrane connectives. Underlayer scales form about 24 longitudinal rows along the flagellum and occur in two distinctive shapes (pentagonal and square). The square shaped underlayer scales are related in position to the attachment sites of the hair-scales. Rod-shaped scales occur in about 20 longitudinal rows along the flagellum and are characteristically positioned as “double scales”. Calcium in the culture medium is necessary to retain rod-shaped scales on the flagellum, absence of calcium or chelation with EGTA or pyrophosphate leads to disappearance of rod-shaped scales from the flagellum. Other divalent cations can only partially substitute for calcium. It is suggested that calcium provides the linkage between underlayer scales and rod-shaped scales inTetraselmis. Flagellar scales inTetraselmis apparently fall into two categories: a) hair-scales (not affected by fixation or absence of divalent cations, firmly bound to axonemal microtubules via the flagellar membrane), b) underlayer scales and rod-shaped scales (affected by fixation and absence of divalent cations, kept on the flagellum mainly by electrostatic forces). The function of flagellar scales inTetraselmis is discussed.
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    Tentacle contraction and ultrastructure inDiscophrya collini: The response to cations (1982)
    Springer
    Protoplasma 112 (1982), S. 92-100 
    Details
    ISSN: 1615-6102
    Keywords: Discophrya ; Tentacle contraction ; Cations ; Calcium ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Discophrya collini is a suctorian protozoan with contractile tentacles containing a microtubule-lined canal and microfilaments. The effects of a range of cations on tentacle contraction and ultrastructure have been determined. Treatment with 80 mM CaCl2 and 95 mM MgCl2 causes contraction to 28% and 57% of the control length respectively. Re-extension takes over 4 hours in the culture medium, but CaCl2-treated tentacles are re-extended after a 5 minutes treatment with 10−2 M EDTA or 5 × 10−3 M EGTA. CuCl2 causes a significant contraction at 10−5 M (to 77%); LaCl3 at 10−4 M (to 65%); ZnCl2 at 10−2 M (to 65%), but BaCl2, CoCl2, MnCl2, NiCl2, and SrCl2 cause significant changes only at 10−1 M. The cytoplasm of CaCl2-treated cells contains two forms of membraneous structures when viewed in TEM; that of MgCl2-treated cells reveals granular areas of medium electron density. None of these features are seen in control cells. The microtubules of the tentacle canal appear to be intact upon its retraction into the cell with no change occurring in the numbers or relative positions of the microtubules. The tentacle cortex is wrinkled. It is suggested from this and previous work that tentacle contraction may be mediated by a microfilament-based mechanism, and that calcium may be involved.
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    The effect of ionophore A 23187 and ruthenium red on tentacle contraction and ultrastructure inDiscophrya collini: Evidence of calcium fluxing from intracellular reservoirs (1983)
    Springer
    Protoplasma 117 (1983), S. 158-166 
    Details
    ISSN: 1615-6102
    Keywords: Calcium ; Contraction ; Discophrya ; Ionophore A 23187 ; Ruthenium red ; Tentacle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The suctorian protozoonDiscophrya collini has contractile tentacles with microfilaments and a central microtubule-lined canal (axoneme). The role of calcium fluxing in tentacle contraction has been investigated using the Ca2+ ionophore A 23187 and ruthenium red (RR), a known inhibitor of certain Ca2+ membrane transport events. Treatment with CaCl2 alone caused tentacle contraction with a threshold at 5 × 10−3 M CaCl2 and a maximum at 5 × 10−2 M CaCl2 with contraction to 32.8% of the original length. In the presence of 5 μM ionophore A 23187 the threshold was lowered to 5 × 10−6 M CaCl2 with a maximum to 19.6% original length at 5 × 10−2 M CaCl2. A 23187 alone induced contraction with a threshold of 3.0 μM and a maximum to 30.5% original length at 10 μM A 23187. Treatment with RR alone had little effect on tentacle length. However, a 10 μM A 23187-induced contraction was partially counteracted by the simultaneous application of RR with a threshold at 2 μM RR and a maximum at 8 μM RR. Removal of the ionophore after induced tentacle contraction resulted in partial re-extension, which was inhibited by RR. Ultrastructural observations indicated that the ionophore and CaCl2-induced contraction processes are indistinguishable. The CaCl2/ionophore treatments led to axonome disruption, interpreted as a consequence of supranormal levels of intracellular Ca2+. X-ray microanalysis of cytoplasmic membrane-bound elongate dense bodies (EDB) showed a high level of Ca2+ in CaCl2-treated cells, little Ca2+ in ionophore-treated cells and intermediate levels in the RR-treated, ionophore/RR-treated and untreated control cells. It is suggested that A 23187 enhances both the uptake of extracellular Ca2+ and the release of Ca2+ from the EDB, the latter being counteracted by RR. These observations support the proposal that the EDB act as Ca2+ reservoirs, and that their Ca2+ fluxing moderates cytosolic Ca2+ levels which mediate a Ca2+-dependent tentacle contraction mechanism.
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    Evidence for the role of Ca2+ ions in tip extension in pollen tubes (1983)
    Springer
    Protoplasma 115 (1983), S. 11-17 
    Details
    ISSN: 1615-6102
    Keywords: Pollen tubes ; Calcium ; Tip extension ; Vesicle fusion ; Microfilaments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pollen tube growth is shown to be inhibited by both suboptimal (〈10−4 M) and supraoptimal (〉10−3 M) Ca2+ ion concentrations. Tip extension rates are independent of Ca2+ ion concentration over the optimal range. Changes in the structure of the tips of pollen tubes after transfer to inhibitory Ca2+ ion conditions provide evidence in support of our proposed mechanism of pollen tube tip growth (J. theor. Biol.98, 15–20, 1982). It is clearly demonstrated that tip extension is controlled, not only by the rate of vesicle fusion, but also by the state of plasticity of the tip; these processes appear to be sensitive to changes in Ca2+ ion concentration.
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    Tentacle contraction inDiscophrya collini: The effects of ionophore A23187 and ruthenium red on Ca2+-induced contraction and uptake of extracellular calcium (1984)
    Springer
    Protoplasma 122 (1984), S. 125-131 
    Details
    ISSN: 1615-6102
    Keywords: Calcium ; Contraction ; Discophrya ; Ionophore A23187 ; Ruthenium red ; Tentacles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The tentacles of the suctorian protozoonDiscophrya collini are stimulated to contract by externally applied Ca2+. The role of extracellular Ca2+ in tentacle contraction was studied by monitoring45Ca2+ uptake, using ionophore A23187 to facilitate membrane transport of calcium and ruthenium red (RR) as an inhibitor of transport. The degree of tentacle retraction was dependent upon external Ca2+ concentration and studies with45Ca2+ using scintillation counting indicated a linear relationship between external Ca2+ concentration and Ca2+ uptake. Uptake of Ca2+ was enhanced in the presence of the ionophore while RR caused little inhibition.45Ca2+ uptake was only partially inhibited by RR when cells were subjected to a Ca2+, ionophore and RR mixture. Grain counts from light microscope autoradiographs after treatment of cells with45Ca2+/ionophore,45Ca2+/RR or45Ca2+ alone showed heavy, light and intermediate labelling respectively. In all instances the grains were evenly distributed within the cell. These observations are interpreted as supporting the suggestion that the ionophore enhances both the uptake of extracellular Ca2+ and release of Ca2+from an internal source, while the RR could only partially prevent movement of Ca2+ through the plasma mebrane. A model is presented suggesting that tentacle retraction is mediated by cytosolic Ca2+ levels which are determined by the fluxing of Ca2+ across the plasma membrane and the membrane of elongate dense bodies which act as internal Ca2+ reservoirs.
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    Calcium-induced fusion of fusogenic wild carrot protoplasts (1984)
    Springer
    Protoplasma 120 (1984), S. 209-215 
    Details
    ISSN: 1615-6102
    Keywords: Fusion ; Calcium ; Protoplast ; Membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Rather than selecting for a chemical fusogen one can select for a fusogenic plant membrane (i.e., one that will fuse readily). Wild carrot suspension culture cells can be grown under conditions which cause the released protoplasts to have a high potential to fuse. Protoplast fusion is enhanced by calcium and inhibited by EGTA. When 10mM calcium (pH6.0) is added, fusion percentages of 60% are common. The mild fusion treatment appears to have no effect on callus regeneration and differentiation.
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    Response to chilling stress in plant cells II. Redistribution of intracellular calcium (1984)
    Springer
    Protoplasma 121 (1984), S. 17-24 
    Details
    ISSN: 1615-6102
    Keywords: Chilling-sensitivity ; Calcium ; Chlortetracyline ; A 23187 ; Lycopersicon ; Digitalis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have investigated the possibility that the rapid low temperature effects upon cyclosis and subcelluar structure might be due to a breakdown in compartmentation of intracellular calcium, leading to an increase in cytoplasmic Ca2+. Changes in fluorescence of chlortetracycline (CTC), a probe for membrane-bound Ca2+ were monitored in the corners of individual trichome cells (effective spot size ca. 800 square microns) with the aid of a Zeiss epifluorescence microscope linked to a Zeiss Zonax analyzing system. A consistent decrease in signal was observed as cells of chilling-sensitiveLycopersicon esculentum Mill. (cv.Ace) were cooled below their threshold temperature for chilling sensitivity. On rewarming, as the temperature rose above the chilling threshold, there was an increase in fluorescent signal. In contrast, trichomes ofDigitalis purpurea (chilling-resistant) showed no such changes. The uncoupling agent, CCCP, and the Ca2+-chelator, EGTA, induced marked decreases in the fluorescent signal in cells from both species. A more direct approach to testing the hypothesis was to examine the effect of modulating cytoplasmic Ca2+ with the aid of the Ca2+ -ionophore A 23187 and a Ca2+ concentration series in EGTA buffer. Above 10−8 M external free Ca2+, streaming began to be inhibited, full inhibition occurring at 5 x 10−6M Ca2+. The strand structure started to disappear when the Ca2+ rose above 10−7M. Disappearance of strands was accompanied by an increase in the number of cells with vesiculated cytoplasm, an effect analogous to that of chilling temperatures on these cells. The phenothiazines, trifluoperazine and chlorpromazine (10−5M) had similar effects. However but such effects were not seen with R 24571 or N(6-aminohexyl)5-chloro-1-napthalenesulfonamide (W 7) until concentrations were reached that orders of magnitude above their IC50 for calmodulin.
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    Calcium localization pattern in clover root hair cells associated with infection process: Studies with aureomycin (1981)
    Springer
    Protoplasma 105 (1981), S. 321-325 
    Details
    ISSN: 1615-6102
    Keywords: Aureomycin ; Calcium ; Fluorescence ; Infection thread ; Root hairs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Localized regions of calcium were shown to change in clover root hair cells after infection withRhizobium trifolii as shown with the Ca++ binding antibiotic, chlorotetracycline. Some root hairs from the immature zone showed increased calcium fluorescence distributed through most of the cell. These root hair had a morphology with a notched side wall, typical of cells infected by bacteria. The maturing root hairs that show a growing infection thread or start of an infection thread, have a similar increased calcium fluorescence, especially around the area of origin of infection thread and tip of the root hair cell.
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    Calcium and magnesium levels in isolated cardiac mitochondria from mice injected with isoproterenol (1981)
    Springer
    Cell & tissue research 215 (1981), S. 13-19 
    Details
    ISSN: 1432-0878
    Keywords: Heart ; Mitochondria ; Isoproterenol ; Calcium ; Magnesium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Calcium (Ca) and Magnesium (Mg) are determined by atomic absorption flame spectrometry in isolated cardiac mitochondria from mice receiving subcutaneous injections of DL-isoproterenol HC1 (ISO), and in mitochondria of untreated controls. In the controls, mitochondria were isolated in the presence or absence of ruthenium red. On the absence of ruthenium red in the isolation medium, mitochondrial Ca levels increase by about 300%, while levels of Mg remain unchanged. Focal myocardial necrosis following a single ISO-injection is shown by electron microscopy. Ca and Mg levels are largely unaffected by a single dose of ISO until 24 h after the injection. A slight increase in Ca occurs in the 48 h samples. When multiple injections of ISO are given every 12th hour for 48 h, 72 h and 96 h, respectively, endogenous Ca and Mg increase significantly. It is suggested that this increase might be associated with ISO-induced cardiac hypertrophy rather than with the pharmacological effects of ISO per se.
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    Multiple effects of Na+ removal on pancreatic secretion in vitro (1980)
    Springer
    Cell & tissue research 210 (1980), S. 295-303 
    Details
    ISSN: 1432-0878
    Keywords: Pancreas ; Stimulus-secretion coupling ; Sodium ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effects of removing Na+ from the incubation medium on basal and secretagogue induced zymogen release by pancreatic fragments and isolated pancreatic acini were studied by both morphological evaluation and measurement of amylase release. In both fragments and isolated acini, removal of Na+ led to an increased basal secretion of zymogen granule contents from acinar cells via exocytosis; secretory material, however, accumulated in acinar and ductular lumina as a result of the lack of fluid secretion necessary to wash out the enzymes. In studies with fragments, after Na+ removal there was no significant increase in amylase release into the medium; isolated acini, in contrast, showed an increased amylase release consistent with the shorter distance from the acinar lumen to the bathing medium. Stimulation with either bethanechol or caerulein led to a further depletion of zymogen granules in both preparations; in the absence of Na+ secretory product accumulated in intracellular lakes as well as in duct lumens. The hypothesis that Na+ influx is important in stimulus-secretion coupling to release intracellular Ca2+ was directly tested by measuring 45Ca2+ efflux. No effect of removing Na+ on 45Ca2+ efflux was seen. It was concluded, therefore, that while Na+ is essential for pancreatic fluid secretion, it is not necessary for the secretion of zymogen granule contents into acinar lumina.
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    Electron-dense precipitates in glomus cells of rat carotid body after fixation in glutaraldehyde and pyroantimonate-osmium tetroxide mixture as possible indicators of calcium localization (1981)
    Springer
    Cell & tissue research 217 (1981), S. 93-104 
    Details
    ISSN: 1432-0878
    Keywords: Carotid body ; Calcium ; Granular vesicles ; Exocytosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An attempt was made to study the subcellular localization of calcium in carotid body glomus cells of adult rats using fixation with glutaraldehyde followed by treatment with a mixture of pyroantimonate and osmium tetroxide. Precipitates were seen as electron-dense particles (EDP) in the glomus cells, mostly within membrane-bound organelles, such as dense-cored vesicles, mitochondria, small clear vesicles, multivesicular bodies, and especially in lysosomes. However, EDP were also seen in the nuclei and in the free cytoplasm of the glomus cells and even outside them. Preincubation of carotid bodies in media containing calcium and either high potassium or calcium-ionophore A 23187 resulted in a marked increase in the general precipitation pattern, there being an increased amount of EDP both in the glomus cell nuclei and in the cytoplasm. Dense-cored vesicles more often showed precipitates than those in the controls. Some dense-cored vesicles contained multiple precipitates, typically located in the electron-lucent area between core and vesicle membrane. Extensive diffusion of ions probably occurred during fixation before precipitation, making the localization of calcium and other precipitating cations unreliable. However, it is possible that precipitates, which were regularly seen in the dense-cored vesicles, may reflect the content of bound calcium. The possible significance of calcium in glomus cell function is discussed, and the need for more adequate methods is emphasized.
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  • 88
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    Distribution of calcium differs in relaxed and contracted myocardial cells of the rat (1981)
    Springer
    Cell & tissue research 221 (1981), S. 295-302 
    Details
    ISSN: 1432-0878
    Keywords: Cardiac muscle cells ; Calcium ; Sarcomere ; Ultrastructure ; Contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Myocardial cells from left ventricles of beating hearts of rats were fixed by immersion in an osmium tetroxide solution containing potassium pyroantimonate to study the electron-microscopic distribution of calcium, the cation being precipitated as an electron-opaque salt (calcium antimonate) by this cytochemical technique. The observed myocytes could be divided into two groups according to their contractile state, evaluated by sarcomere length measurements. In contracted cells (mean sarcomere length 1.43 μm) the intramyoflbrillar precipitate was confined to areas of I-bands bordering the A-bands, the intermyofibrillar space showing scarce content in reaction product. Relaxed cells (mean sarcomere length 1.69 μm) presented a heavy deposition of reaction product over the sarcomeres, the electron-opaque dots being absent on the H and Z bands. The sarcotubular system and mitochondria were also clearly marked by the reaction product. This second pattern of calcium distribution has not been previously described in heart muscle cells and is interpreted as corresponding to the phase of rise of intracellular calcium which is mediated by membrane depolarization. Our results suggest that different bands of heart sarcomeres show different abilities to bind calcium. The I bands retain the cation even in cells under sustained contraction, probably due to their content in calmodulin; Z and M bands are apparently not involved in calcium sequestration, whereas the content in calcium of the A bands seems to be dependent on the contraction-relaxation cycle of heart myocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216733
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  • 89
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    Calcium dynamics, exocytosis, and membrane turnover in the ovulation hormone-releasing caudo-dorsal cells of Lymnaea stagnalis (1983)
    Springer
    Cell & tissue research 233 (1983), S. 143-159 
    Details
    ISSN: 1432-0878
    Keywords: Calcium ; Exocytotic hormone release ; Membrane resorption ; Mitochondria ; Lymnaea stagnalis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The axon terminals of the neuroendocrine caudo-dorsal cells (CDC) of the freshwater snail Lymnaea stagnalis release an ovulationstimulating hormone by exocytosis in a calcium-dependent way. Ultrastructural studies of the terminals, involving the K-pyroantimonate method for the demonstration of calcium and control tests with EGTA, show that calcium occurs in mitochondria and in various types of vesicular structure. Quantitative investigations indicate that mitochondria accumulate calcium during a short period of high neurohormone-release activity (“active state”; ca. 45 min) and release it again into the axoplasm some hours later, during a period of low secretory activity (“resting state”). Probably, in this way mitochondria play an important role in the buffering of the axoplasmic calcium concentration during high hormone-release activity. HRP-incorporation studies strongly suggest that the calcium-containing vesicular structures constitute a mechanism of membrane sequestration by which the CDC axon terminals resorb, transform, and release parts of the axolemma after exocytotic hormone release. The results furthermore indicate that this mechanism also may be involved in the control of the calcium concentration of the axoplasm, by taking up calcium from the axoplasm and releasing it into the extracellular space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222239
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  • 90
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    Endoplasmic reticulum whorls as a source of membranes for early cytaster formation in parthenogenetically stimulated sea urchin eggs (1984)
    Springer
    Cell & tissue research 236 (1984), S. 237-244 
    Details
    ISSN: 1432-0878
    Keywords: Aster formation ; Calcium ; Endoplasmic reticulum ; Hypertonic stress ; Parthenogenetic stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Sea urchin eggs exposed to a continuous hypertonic treatment rapidly form many concentric whorls of endoplasmic reticulum (ER) during the pre-activation period of the parthenogenetic development. These whorls, however, are only a temporary configurational alteration of ER which begin to break up just prior to egg activation. The conversion back to normal vesicles and lamellae occurs not only concurrently with the appearance of early cytastral areas, but also frequently in close association with the formation of these membranous areas. It is revealed here that membrane elements from disrupting whorls may become incorporated into adjacent, developing clear areas, early cytastral areas, and that this ER constitutes an initial major source of membranes for these early astral areas. Having previously suggested that the actual formation of ER whorls occurs in direct response to released intracellular calcium in hypertonic stressed eggs, the new findings, along with other related data and correlations, further suggest that whorl disruption and the formation of associated astral areas can be correlated with a corresponding decrease in the concentration of this released calcium in the cytoplasm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216536
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  • 91
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    Specific effect of calcium ions on the calcium-sensitive cells of the pars intermedia in the goldfish (1981)
    Springer
    Cell & tissue research 214 (1981), S. 23-31 
    Details
    ISSN: 1432-0878
    Keywords: Pituitary ; Pars intermedia ; Calcium ; Deionized water ; Teleosts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Cytological changes in the calcium-sensitive (Ca-s) cells (formerly termed PAS-positive cells) of the pars intermedia were investigated in the goldfish after adaptation to deionized water (DW), with or without addition of sodium, potassium and magnesium. These ions were added as chloride salts at concentrations similar to those present in fresh water (FW). The marked stimulation of the Ca-s cells is not inhibited in DW supplemented with Na+ (0.35 mM/1), K+ (0.05 mM/1), and Mg2+ (0.2mM/1) for a period of 24 days. The inhibition of the response to DW with calcium chloride (2 mM/1) is reproduced with calcium formiate (2 mM/1). These data show that chloride ions are not responsible for the regression of the Ca-s cells observed in goldfish kept in DW supplemented with calcium chloride. The effect of calcium ions on the Ca-s cells appears to be specific. These results support the hypothesis that the Ca-s cells synthesize a factor (hypercalcin?) involved in calcium regulation, and that its release is influenced by the calcium content of the environment. The role of the pars intermedia in calcium metabolism is strengthened by the present results. Biochemical data suggest the presence of a hypercalcemic factor in the pituitary of fish (Parsons et al. 1978) and are in agreement with the present cytological findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235141
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  • 92
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    Cytochemical localisation of calcium binding sites in adrenal chromaffin cells and their relation to secretion (1983)
    Springer
    Cell & tissue research 229 (1983), S. 207-217 
    Details
    ISSN: 1432-0878
    Keywords: Exocytosis ; Secretion ; Calcium ; Chromaffin cells ; Adrenal medulla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructural localisation of calcium in the chromaffin cells of the adrenal medulla was investigated using the pyroantimonate technique. The electron-dense precipitate resulting from processing in the presence of pyroantimonate was removed by treatment of sections with 2 mM EGTA suggesting that the pyroantimonate technique was localising calcium since this chelator shows a 1000∶1 preference for Ca2+ over Mg2+. Using dissociated cells from the bovine adrenal medulla, calcium was localised in control cells and in cells stimulated with 1 mM carbamylcholine for 1, 10 and 30 min. Stimulation resulted in an increase in plasma membrane-associated calcium within 1 min. Much of this calcium was localised at sites of granule-plasma membrane interaction and was also seen at sites of coated-vesicle formation at longer periods of stimulation. Membrane-bounded vacuoles, appearing in cells stimulated for 10 or 30 min, also showed associated electron-dense precipitate. The results obtained are consistent with a role for the calcium ion as a mediator in exocytosis at the stage of granule-plasma membrane fusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217893
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  • 93
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    Cytological effects of ionophore-induced stimulation on the exocrine pancreas of the rat (1984)
    Springer
    Cell & tissue research 235 (1984), S. 699-701 
    Details
    ISSN: 1432-0878
    Keywords: Ionophore A-23187 ; Calcium ; Exocrine pancreas ; Secretion ; Zymogen granule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rat-pancreas lobules were incubated with the ionophore A-23187 in the presence of Ca2+. After 90 min, some of the acini were partially or almost completely depleted of their zymogen granules while others had the appearance of resting acini. With few exceptions, the cells of a given acinus were degranulated to a comparable level. Slight dispersion of the zymogen granules was noticed in cells incubated in a Ca2+-free medium containing EGTA with or without A-23187. In the presence of Ca2+ the secretory response obtained with the ionophore was comparable to that observed with 10-5M urecholine. The results obtained provide cytological evidence that the secretory response is only partially determined at the membrane-receptor level and that other mechanisms intervene between cytosol Ca2+ increase and exocytosis.
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    URL: http://dx.doi.org/10.1007/BF00226972
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  • 94
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    Pinocytosis and locomotion of amoebae (1980)
    Springer
    Cell & tissue research 213 (1980), S. 9-20 
    Details
    ISSN: 1432-0878
    Keywords: Pinocytosis ; Calcium ; Chlorotetracycline ; Fluorescence microscopy ; Amoeba proteus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The dynamics of Ca++ during induced pinocytosis were studied in Amoeba proteus using chlorotetracycline (CTC). The fluorescence of the Ca++ -CTC-complex was monitored by an image intensification system, which has certain advantages over standard equipment: (1) Living cells are not subjected to the damaging influence of intensive microscopic illumination, (2) fluorescent probes are not bleached during observation, and (3) the rapid dynamics of Ca++-fluxes can be recorded using short exposure times. The results demonstrate the existence of Ca++ bound to intracellular and extracellular sites of the cell membrane complex in normal locomoting and pinocytoting Amoeba proteus. The application of cations inducing pinocytosis causes a rapid decrease in the external CTC-fluorescence probably due to a release of Ca++ from the mucous layer. The degree of fluorescence intensity is correlated with the capacity of pinocytotic channel formation, i.e., the fluorescence decreases as the number of channels increases. During the phase of vesiculation a distinct fluorescence mainly restricted to the basal region of the channels is observed. Intracellular Ca++ was detected in close vicinity to the plasma membrane after both microinjection and external application of CTC. The internal CTC-fluorescence is slightly decreased during the induction phase of pinocytosis. The observations are in good agreement with previous results on the localization of Ca++-binding sites at the plasma membrane of Amoeba proteus and demonstrate the important role of Ca++-fluxes for the process of pinocytosis.
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    URL: http://dx.doi.org/10.1007/BF00236916
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  • 95
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    Disruption of insect photoreceptor membrane by divalent ions: Dissimilar sensitivity of light- and dark-adapted mosquito rhabdomeres (1981)
    Springer
    Cell & tissue research 216 (1981), S. 403-411 
    Details
    ISSN: 1432-0878
    Keywords: Photoreceptors ; Calcium ; Fixation artifact ; Light-adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The conditions that lead to the formation of myelin figures in rhabdomere microvilli were studied in the larval ocelli of the mosquito Aedes aegypti. These artifacts can result from the addition of divalent ions, such as Ca2+, to primary-aldehyde fixatives, but they form subsequently during postfixation with OsO4. In light-adapted ocelli, myelin figures are concentrated at the proximal ends of the microvilli along the cytoplasmic margin of the rhabdomere. The severity of the artifact is proportional to the ion concentration: scattered myelin whorls are induced by Ca2+ concentrations as low as 5 mM; they become abundant at 15 mM to 25 mM, and displace much of the rhabdomere margin at 50 mM. In contrast, even at high concentrations of Ca2+ few membrane whorls form in dark-adapted rhabdomeres, and these are mostly located at the distal ends of the microvilli. The differential response of the rhabdomere microvilli in light and darkness does not result from a direct action of light during fixation; it reflects an underlying difference between light- and dark-adapted photoreceptor membranes. We suggest that this differential sensitivity to divalent ions is associated with the shedding of membranes from the rhabdomere, a process that is enhanced by light and reduced in darkness.
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    URL: http://dx.doi.org/10.1007/BF00233627
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  • 96
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    Cytochemical analysis of intracellular calcium distribution in the anterior pituitary of the rat (1981)
    Springer
    Cell & tissue research 220 (1981), S. 191-200 
    Details
    ISSN: 1432-0878
    Keywords: Rat ; Pituitary ; Calcium ; Pyroantimonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In an attempt to assign morphologic identities to previously distinguished functional calcium compartments in the anterior pituitary of the rat, we employed the potassium pyroantimonate technique for cation localization. Tissues were incubated for In at 37°C in control medium; with 10mM theophylline; or with depolarizing amounts of potassium. Precipitate was quantified on photomicrographs of tissue prepared for electron microscopy with a Talos Systems Digitizer. The nature of the electron dense precipitate was dependent on the experimental state of the tissue. Treatment with 5 mM EGTA abolished the dense precipitate. Electron microprobe analysis also confirmed that calcium was the predominant cation in the observed precipitate. The most significant changes in precipitate deposition occurred along the plasma membrane, the limiting membrane of secretory granules and within mitochondria. Dense precipitate was present along the plasma membrane only in cells treated with potassium. Control tissue exhibited higher levels of precipitate associated with the limiting membrane of secretory granules than either theophylline-treated or potassium-treated tissue. Mitochondria contained more precipitate in potassium-treated tissue than in controls; the mitochondria of theophylline-treated tissue contained intermediate levels of precipitate. Addition of either theophylline or depolarizing amounts of potassium has been associated with hormone secretion in anterior pituitary tissue of normal rats. Kinetic studies in our laboratory indicate that intracellular calcium shifts occur. The pyroantimonate technique is useful in verifying morphologically the calcium compartments involved in shifts in intracellular calcium.
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    URL: http://dx.doi.org/10.1007/BF00209977
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  • 97
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    PAS-positive cells of the pars intermedia are calcium-sensitive in the goldfish maintained in a hyposmotic milieu (1980)
    Springer
    Cell & tissue research 212 (1980), S. 29-38 
    Details
    ISSN: 1432-0878
    Keywords: Pituitary ; Pars intermedia ; Calcium ; Deionized water ; Teleosts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Cytological changes in the pars intermedia of the goldfish were investigated after adding calcium to deionized water (DW). In fish maintained in DW, the PAS-positive cells are highly stimulated in comparison to cells of fish kept in fresh water (FW). In DW supplemented with calcium at the same concentration as in FW (2 mM/l), the hyperactivity of the PAS-positive cells is prevented. When calcium ions are added 60 h before the animals are sacrificed, the PAS positive cells start to show signs of regression and their granules are stored: the release of the granular material appears to be suppressed by calcium. In the goldfish, the PAS-positive cells, homologous to a similar cell type in the eel, react only very weakly with the PAS technique. The name “calcium-sensitive cells” appears to be more appropriate in the goldfish for this particular cell type, secreting an unknown factor. This factor, different from the prolactin produced in the rostral pars distalis of the hypophysis, might be an equivalent of a “hypercalcin”.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234030
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  • 98
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    The demonstration of calcium in the axonal granules of the peripheral nervous system of male Schistosoma mansoni by X-ray microanalysis (1982)
    Springer
    Cell & tissue research 222 (1982), S. 597-604 
    Details
    ISSN: 1432-0878
    Keywords: Schistosoma mansoni ; Freeze-dried cryosections ; X-ray microanalysis ; Calcium ; Peripheral nervous system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A conspicuous feature of freeze-dried cryosections of male Schistosoma mansoni is the presence of groups of electron-dense granules. X-ray analysis in the TEM of these granules shows them, in comparison with the adjacent cytoplasm, to contain significantly greater amounts of sodium and calcium. In glutaraldehyde-fixed material, these granules have been correlated with the membrane-bounded, electron-dense granules found within the axons of the peripheral nervous system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213857
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